European Journal of Inorganic Chemistry - Current Research Articles
Current research articles: Inorganic Chemistry
The author- or copyrights of the listed research articles below
are held by the respective authors or site operators, who are also
responsible for the content of the presentations.
More current articles from Chemistry Journals same topic: see
the navigation menu on the left.
To list your article here please contact us by eMail.
To search this web page for specific words type "Ctrl" +
"F" on your keyboard (Command + "F" on a Mac). Then: type the word
you are searching for in the window that pops up!
On this page considered journals:
European Journal of Inorganic Chemistry - published by Wiley-VCH
EurJIC is the fastest growing journal in inorganic chemistry. It publishes Full Papers, Short Communications, and Microreviews from the entire spectrum of inorganic, organometallic, bioinorganic, and solid-state chemistry.
The equal molar reaction of Cu(BF4)2·3H2O with the ditopic, bis(pyrazolyl)methane ligand p-[CH(pz)2]2C6H4 (Lp) where pz is a pyrazolyl ring, in methanol produces [Cu(?-Lp)(CH3OH)](BF4)2·(CH3OH)0.62 (1) and a similar reaction in water/methanol yields [Cu(?-Lp)(CH3OH)]2(SiF6)(BF4)2·(CH3OH)2 (2). The water/ethanol solvent system yields both [Cu2(?-Lp)(H2O)6](SiF6)2·(H2O)4 (3) and [Cu(?-Lp)(H2O)](BF4)2·(CH3CH2OH)2 (4), and if the ratio of Cu(BF4)2·3H2O and Lp is changed to 2:1, only 3 forms. Recrystallization of the solid formed from the reaction of THF solutions of Cu(BF4)2·3H2O with Lp from DMSO yields [Cu2(?-Lp)(DMSO)6](BF4)4·(DMSO)2·C6H6·(H2O)0.5 (5) and a recrystallization of compound 1 from DMSO yields [Cu2(?-Lp)(DMSO)6](BF4)4·(DMSO)2·C6H6 (6). Complexes 1, 2, and 4 are coordination polymers in which the N4O-coordinated, square-pyramidal copper(II) ions are oriented in an anti conformation withrespect to the phenylene spacer of Lp. Complexes 3, 5 and 6 are dinuclear with N2O3-coordinated, square-pyramidal copper(II) ions again oriented in an anti configuration with respect to the bridging Lp. The square pyramidal geometries show axial elongation, a result of pseudo Jahn–Teller electronic effects. In the cases of the coordination polymers, the axially coordinated solvent molecule is lost at low temperatures upon heating of the crystals. The three compounds in each structural type have nearly the same overall configurations. Cooperative effects of O–H···F, O–H···O and C–H···F hydrogen bonding interactions organize the supramolecular structures and influence the crystal packing of complexes 1–4. The C–H···F interactions have metrics that indicate they are unusually strong, due to the enhanced polarization of the C–H bond and charge assistance from the anionic fluorine atom.The bitopic ligand p-[CH(pz)2]2C6H4 (Lp) forms two types of complexes with Cu(BF4)2·3H2O: coordination polymers of the formula [Cu(?-Lp)(solvent)]2+ and dinuclear [Cu2(?-Lp)(solvent)6]4+, where the copper(II) ions are in a square pyramidal geometry and are oriented in an anti conformation. Hydrogen bonding interactions organize the supramolecular structures.
The design and synthesis of an intensely blue rhodium(III) complex [3]+ of a new N,N-donor ligand, 8-(quinolin-8-ylamino)pyrido[2,1-c][1,2,4]benzotriazin-11-ium, [2]+, which contains a planar pendant triazinium arm, is described. Structural characterization for [3]+ was carried out by using various spectroscopic techniques and single-crystal X-ray crystallography. The organometallic rhodium(III) compound shows a ligand-based reversible reduction at –0.65 V. The electrochemically reduced compound displays a single-line EPR spectrum that signifies the formation of ligand-based free radicals. Compound [3]+ shows a binding propensity to calf thymus DNA to give a Kapp value of 6.05?×?105M–1. The parent triazinium salt, pyrido[2,1-c][1,2,4]benzotriazin-11-ium [1]+ and the ligand salt [2]+ exhibit photoinduced cleavage of DNA in UV-A light, whereas the reference Rh complex [3]+ photocleaves DNA with red light (647.1 nm). The compounds show photonuclease activities under both aerobic and anaerobic conditions. Mechanistic investigations under aerobic conditions with several inhibitors indicate the formation of hydroxyl radicals by means of a photoredox pathway. Under anaerobic conditions, it is believed that a photoinduced oxidation of DNA mechanism is operative. Compound [3]+ exhibits photocytotoxicity in HeLa cervical cancer cells to give IC50 values of (12?±?0.9) ?M in UV-A light at 365 nm and (31.4?±?1.1) ?M in the dark.The design and synthesis of an intensely blue rhodium(III) complex, which appears to be a promising photochemotherapeutic agent, is described.
The site-directed generation of a heterodinuclear FeIIICuII complex by using a new asymmetric dinucleating ligand FloH is reported. The iron(III) ion is introduced first on the preferential metal-binding site of the ligand that leads to the formation of the thermodynamically favored five-membered chelate rings upon metal-binding. Copper(II) is introduced in the next step. The stepwise metalation strategy reported here may be extended to the preparation of other heterometallic complexes with the view of avoiding a statistical distribution. Such complexes can offer novel spectroscopic properties, electronic structures, and reactivities in comparison to their homometallic analogues.The synthesis of a new asymmetric dinucleating ligand FloH, designed with two sets of metal ion binding groups suited to selective complexation, is reported. The site-directed generation of a heterodinuclear FeIIICuII complex is performed in highyield and purity by using FloH.
A series of neutral pentacoordinate silicon(IV) complexes with an SiFO2NC, SiBrO2NC, SiO2NC2, SiO2N2C, SiFON2C, SiBrON2C, SiON2C2, or SiON3C skeleton was synthesized and structurally characterized by multinuclear NMR spectroscopy in the solid state and in solution and by single-crystal X-ray diffraction. The compounds studied contain a tridentate dianionic O,N,O or N,N,O ligand, a phenyl ligand, and a (pseudo)halogeno ligand (F, Br, CN, N3, NCS). The structures, NMR spectroscopic parameters, and chemical properties of these silicon(IV) complexes were compared with those of related compounds that contain an analogous tridentate dianionic S,N,O ligand instead of the O,N,O or N,N,O ligand (comparison of S/O/NMe analogues). In addition, two cationic pentacoordinate silicon(IV) complexes with an SiO2N2C and SiON3C skeleton, respectively, were synthesized (isolated as iodides) and structurally characterized. These compounds contain a tridentate O,N,O or N,N,O ligand, a phenyl ligand, and an acetonitrile ligand. The experimental investigations reported in this article were complemented by computational studies to better understand the different properties of some of the S/O/NMe analogues studied.A series of neutral pentacoordinate silicon(IV) complexes was synthesized and structurally characterized by NMR spectroscopy (solid state and solution) and single-crystal X-ray diffraction. The compounds studied contain a tridentate dianionic O,N,O or N,N,O ligand, a phenyl ligand, and a (pseudo)halogeno ligand (F, Br, CN, N3, NCS). These complexes were compared with related compounds that contain a tridentate dianionic S,N,O ligand.
Three dinuclear MnIII compounds [{Mn(H2O)(NN)}2(?-3-ClC6H4COO)2(?-O)]X2 with NN = 2,2?-bipyridine (bpy; 1 and 2) or 1,10-phenanthroline (phen; 3) and X = NO3– (1) or ClO4– (2 and 3) have been synthesized. The X-ray structures of compounds 1 and 3 were solved and the magnetic properties of the three compounds analyzed. Compounds 1 and 3 showferromagnetic coupling, the J values being 11.8 and 5.7 cm–1,respectively. Compound 2 displays weak antiferromagnetic behavior with a J value of –0.23 cm–1. The catalase activity of these three compounds and that of eight analogous dinuclear MnIII compounds with 2- and 4-chlorobenzoato ligands has been investigated. The presence of different ligands and counteranions allowed the analysis of their effects on the catalytic activity. It was observed that compounds with perchlorate anions show higher activity than compounds with nitrate anions and compounds with 3-chlorobenzoato ligands are the worst catalysts. Moreover, most of these compounds show higher conversions than other compounds with analogous structures.The catalytic efficiency of 11 dinuclear MnIII compounds with chlorobenzoato ligands has been studied for the disproportionation reaction of H2O2. The presence of different ligands and counteranions allowed the analysis of their effects on the catalytic activity.
ortho-Metalated iridium(III) complexes were synthesized in the supercages of faujasite-type zeolites by a microwave-assisted ship-in-a-bottle procedure. IrIII was inserted by means of ion exchange followed by the addition of 2-(2,4-difluorophenyl)pyridine (dfppyH) or 2-phenylpyridine (ppyH), demonstrating the first example of iridium–carbon sigma bond formation in zeolite cages. These zeolite powder samples containing IrIII complexes showed relatively high luminescence quantum yields [14.34?% for Ir(dfppy)3 and 4.76?% for Ir(ppy)3]. 2-Phenylquinoline (phqH) afforded the corresponding ortho-metalated complex that formed on the outer surface of the zeolite particles, because its large size prevented it from entering the supercages. The color of the emission from the zeolite powder samples could be tuned in a range from blue to green by the successive reaction of IrIII ions in the zeolite with the two ligands dfppyH and ppyH, leading to the formation of two individual types of complexes, Ir(dfppy)3 and Ir(ppy)3, in the supercages of the zeolite, which was confirmed by the characteristic emission spectrum of each complex.Iridium–carbon sigma bond formation in supercages of faujasite-type zeolites is achieved by using a microwave-assisted ship-in-a-bottle synthesis. The successive reaction of IrIII cations in the zeolite with two ligands leads to two types of complexes in the different supercages, and the emission from these IrIII complexes can be tuned in a range from blue to green.
Tricarbonylmanganese(I) complexes of the ligands tris(imidazol-4-yl)phosphane (4-tipH), tris(1,4-diisopropylimidazol-2-yl)phosphane (2-tipiPr2), tris(pyridin-2-yl)phosphane (tpp) and tris(N-methylimidazol-2-yl)carbinol (2-ticNMe) were prepared. These act as N,N,N tripodal chelators. The solid-state structure of [Mn(CO)3(tpp)]OTf was determined by X-ray diffraction. The potential of these complexes to act as photoactivatable CO-releasing molecules (PhotoCORMs) was studied with the UV/Vis spectroscopy-based myoglobin assay as well as by time-resolved IR spectroscopy. Within the series of compounds prepared, the steric bulk of the imidazolyl groups seems to significantly influence the CO-release kinetics and stoichiometry when using the myoglobin assay. In contrast, the time-resolved IR data suggest release of all carbonyl ligands upon irradiation. This effect points to a much closer association of myoglobin and PhotoCORMs than previously thought and will require further investigation.CO-releasing molecules are interesting therapeutic agents that can deliver and release CO upon stimulation. Light triggers the release of CO in different complexes [LMn(CO)3]+, where L is an N,N,N ligand. Although different amounts of CO released per complex are observed by myoglobin assay, IR spectroscopic investigation of their solutions indicates loss of all CO ligands.
Epoxidations with methyltrioxorhenium(VII) (MTO) as catalyst precursor and additives are examined in fluorinated solvents under various conditions. These fluorinated solvents have a strong influence on the 1H NMR, 13C NMR, and 17O NMR spectroscopic data of the catalyst precursor, apparently contributing significantly to the catalytic activity of such systems. Accordingly, the highest turnover frequencies (TOF) obtained with MTO-containing systems have been determined, reaching up to 39000 h–1. Despite the high initial activity, such systems show a pronounced sensitivity to water leading also to faster catalyst decomposition. The high activity as well as the high sensitivity of the catalyst may be due to its solvent-enhanced higher Lewis acidity, leading to quantitative epoxide yields only when quite stable epoxides are the end products and very high amounts of Lewis base additives are applied.Methyltrioxorhenium(VII)-catalyzed epoxidation of cyclooctene in fluorinated solvents is examined. Trifluoroethanol and hexafluorisopropanol are the most commonly used fluorinated solvents. Pyrazole and 4-tert-butylpyridine are additives of equal quality. For the first time, quantitative yields are achieved with a methyltrioxorhenium loading of only 0.01 mol-%.
AgCl nanoparticles with a diameter of 50–100 nm were synthesized in ethylene glycol with the assistance of poly(vinylpyrrolidone) at room temperature. A photoactivation process was then introduced by exposing the as-obtained AgClnanoparticle solution to common fluorescent lamp or direct sunlight irradiation to form a uniform layer of Ag nanoparticles (5–10 nm) on the surface of the AgCl nanoparticles. The AgCl/Ag nanocomposites showed higher visible light photocatalytic activity for decomposing organic pollutants [such as methyl orange (MO), methyl blue (MB), and rhodamine B (RhB)] under the irradiation of common fluorescent lamp or direct sunlight. Recycle photocatalysis experiments indicated that the AgCl/Ag nanocomposite exhibited higher stability. Moreover, the AgCl/Ag nanocomposites showed better antibacterial properties on Escherichia coli, Staphylococcus aureus, and Bacillus subtilis.AgCl/Ag nanocomposites were fabricated by a simple photoactivation process. A uniform layer of Ag nanoparticles (5–10 nm) was formed on the surface of AgCl nanoparticles (50–100 nm) by irradiation with a fluorescent lamp or direct sunlight. The AgCl/Ag nanocomposites show higher visible light photocatalytic activity for decomposing organic pollutants under the irradiation of common fluorescent lamp or direct sunlight. They also show better antibacterial properties.
Two isostructural polyoxotungstates, K6Na4H8[Eu6(H2O)38(P2W15Nb3O62)4]·45H2O (1) and K6Na4H8[Ce6(H2O)38(P2W15Nb3O62)4]·56H2O (2), have been synthesized by reactionof saturated Nb/W mixed-addendum polyoxometalate [P2W15Nb3O62]9– and lanthanide ions in acidic solution. They are the first examples of lanthanide derivatives based on saturated Dawson-type Nb/W mixed-addendum polyoxometalates. All the compounds were fully characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, elemental analysis, and electrochemistry. XRD analysis reveals that 1 and 2 display one-dimensional chains constructed from sandwich-type fragment {Ln3(P2W15Nb3O62)2} linked by alternating Ln–O–W bridging bonds. In 1 and 2, all the lanthanide ions selectively bind to Ot(Nb) of {P2W15Nb3O62} fragments (Ot: terminal oxygen atoms), indicating the high nucleophilicity of Ot(Nb). The photoluminescence behavior of 1 in the solid state was investigated at room temperature; it exhibits the characteristic transition of Eu under the excitation wavelength (394 nm). Additionally, the cyclic voltammogram of 2 indicates good electrocatalytic activity towards the reduction of nitrite.Two isomorphic POMs are constructed by [P2W15Nb3O62]9– and lanthanide ions (Eu3+ for 1 and Ce3+ for 2) as a result of the high nucleophilicity of Ot(Nb). The formation of Ln–O–Nb and Ln–O–W bridging bonds results in 1D architectures. The photoluminescence behavior of 1 and electrocatalytic activity of 2 have been studied.
New charged cyclometalated iridium(III) complexes [Ir(ppy)2(L)](PF6) [ppy = 2-phenylpyridine; L = bis(pyrazol-1-yl)methane (for 1); L = bis(3,5-dimethylpyrazol-1-yl)methane (for 2)] were synthesized and their electrochemical and photophysical properties studied. These complexes with non-?-electron-conjugated ancillary chelates exhibit significantly blueshifted emission relative to those of commonly used derivatives with NN ancillary ligands such as bipyridine or phenanthroline. Both X-ray and theoretical analysis based on time-dependent density functional theory (TD-DFT) reveal that the binding of Ir to the bis(pyrazol-1-yl)methane ancillary ligand is much weaker than that to the phenylpyridine main ligand; the effect is enhanced in the excited state. As a result, the ancillary ligand does not participate in low-energy excitations and triplet emission, and the electronic transitions are concentrated on the main chromophoric ligands. The blueshift feature is attributed to emission originating from the main cyclometalated ligands, in contrast to emitters with the NN chromophoric ancillary ligand. In addition, complex 2 exhibits a one order of magnitude higher non-radiative decay rate than complex 1, which is attributed to the steric hindrance of the methyl groups that leads to a more loosely bound ancillary ligand.The bis(pyrazol-1-yl)methane ancillary ligand induces a blueshift in the emission of charged cyclometalated iridium(III) complexes. In addition, the nonradiative rate constant increases by one order of magnitude when the ligand is substituted with methyl groups, which induce some steric hindrance and lead to a more loosely bound ancillary ligand.
The preparation of the secondary phosphane (Ph){C6H3-2,6-(CH2NMe2)2}PH (1), a potentially base-stabilized ligand, and the sterically protected carbaborane-based phosphane (o-CH3C2B10H10)2PH (2) is reported. Reaction of Sn{N(SiMe3)}2 with 1 gives the diphosphastannylene [(Ph){(C6H3-2,6-CH2NMe2)2}P]2Sn (3) in high yield. In contrast, the room-temperature reaction of 2 with Sn{N(SiMe2)}2 does not proceed. By applying elevated temperatures, the heteroleptic amidophosphastannylene {(o-CH3C2B10H10)2P}{(SiMe3)2N}Sn (4) was formed, instead of the expected diphosphastannylene {(o-CH3C2B10H10)2P}2Sn. The thermal decomposition of compounds 3 and 4 was also studied. The thermal decomposition of 3 produced the new phosphorus–phosphorus-bonded compound 5, an unprecedented 1,2-diphosphol-type molecule.Synthesis of diphosphastannylene [(Ph){C6H3-2,6-(CH2NMe2)2}P]2Sn and heteroleptic amidophosphastannylene {(o-CH3C2B10H10)2P}{(SiMe3)2N}Sn is reported. The thermal decomposition of [(Ph){C6H3-2,6-(CH2NMe2)2}P]2Sn produced an unprecedented 1,2-diphosphol-type molecule.
The back cover picture highlights the mechanical and optical properties of a hybrid silica-PHEMA coating on glass reinforced by using goethite nanorods in relation with the local structure at the interface. We demonstrate the possibility to finely tune the final mechanical properties by adjusting the coating silica content. In this hybrid nanocomposite, goethite particles exhibit interesting stress relaxation functions, which prevent crack formation in the films whilst reaching high silica content in the hybrid matrix. Details are discussed in the article by N. Chemin, C. Chanéac et al. on p. 2675 ff.
The front cover picture shows a schematic representation of the coordination network and the temperature dependence of magnetization of a cyano-bridged V–Nb bimetal assembly, K0.59VII1.59VIII0.41[NbIV(CN)8]·(SO4)0.50·6.9H2O. This compound exhibits ferrimagnetism with a high Curie temperature (TC) of 210?K. This temperature is the highest TC value among those of octacyano-bridged bimetal assemblies. The Short Communication by S. Ohkoshi et al. on p. 2649 ff. demonstrates that the increase in the superexchange pathways of VII–NC–NbIV contributes to the achievement of the high TC value.
The use of microwave heating for the synthesis of (N-heterocyclic carbene)-bearing complexes of Cu, Ag and Au allows for a drastic reduction of the reaction times required by conventional heating, while affording comparable or better yields of the desired complexes.The use of microwave heating for the direct synthesis of (NHC)MCl complexes (NHC = N-heterocyclic carbene; M = Cu, Ag, Au) in very short reaction times is presented. Comparable or better yields than those reported by using conventional heating can be obtained with this protocol.
To identify the chemical species involved in a unique, vanadium-based chemical oscillator reaction, products derived from indole in the oscillation solution were isolated and characterized. NMR and mass spectra showed that 3,3-dichloro-2-oxoindole and isatin were formed during the oscillation process. The formation of these two compounds suggests that peroxo species such as CHCl2OO· and CHCl2OOH play a key role in the construction of the oscillation system. A skeletal model for the system is proposed based on these findings.Products derived from indole in a vanadium-based oscillation solution were identified to be 3,3-dichloro-2-oxoindole and isatin. Peroxo species such as CHCl2OO· and CHCl2OOH were found to play a key role in the construction of the chemical oscillation system. A skeletal model for the oscillation reaction is proposed.
A novel method to prepare TiO2-coated Ag nanowire arrays for use as multifunctional surface enhanced Raman scattering (SERS) active substrates is introduced. Such an array is made by the synthesis of an Ag nanowire array utilizing an anodic aluminum oxide (AAO) template, followed by coating of the Ag wires with a layer of titania that is several nanometers thick. Employing these TiO2-coated Ag nanowire substrates in the detection of organic contaminants allows high SERS enhancement to be achieved. Moreover, owing to the high photocatalytic activity of titania, the substrate can degrade target molecules into small inorganic molecules under UV irradiation, and in this manner the arrays are able to self-clean. The unique properties of this integrated substrate enable it to exhibit its feasibility as an analytical tool for the assessment of environmental pollution and thus to assist in the detection and disposal of contaminants.A novel method to prepare TiO2-coated Ag nanowire arrays for use as multifunctional surface-enhanced Raman scattering (SERS) active substrates is introduced. Employing this substrate for the detection of organic contaminants can lead to high SERS enhancement. Owing to the high photocatalytic activity of TiO2, the substrate can degrade target molecules into small inorganic molecules, and in this way the arrays are able to self-clean.
Redox and coordination processes are coupled in the course of reactions of the organic electron donors 1,2,4,5-tetrakis(tetramethylguanidino)benzene (1) and 1,2,4,5-tetrakis(N,N?-dimethyl-N,N?-ethyleneguanidino)benzene (2) with silver salts. Experiments with several different silver salts show that the product structure is significantly affected by the properties of the anion in these salts. Chain polymers are the products of reactions with AgPF6 or AgBF4, in which dicationic organic building blocks are connected by silver ions. Experiments with AgNO3 yielded either dinuclear complexes (with 1) or 2D networks (with 2). If the salt Ag[Al{OC(CF3)3}4], featuring a weakly coordinating anion, was used, simple silver-free salts of the guanidine dication were obtained. The thermal stability, optical properties, and electrical conductivity were studied in detail for the product polymer {[(1)Ag](PF6)3}n. From the temperature dependence of the electric conductivity, this compound was found to be a semiconductor with a band gap of approximately 3 eV. The experiments were complemented by quantum chemical calculations at density-functional-theory level on the band structure of this and a related polymer. The electronic situation was further analyzed with the aid of molecular model complexes, which were either synthesized or calculated.1D coordination polymers of oxidized guanidino-functionalized aromatic ligands were prepared by coupled oxidation and coordination with silver salts. The structures and electronic properties of these semiconducting materials were analyzed.
Two new hybrid ligands that exhibit organic as well as siloxane chains between four phosphorus atoms in bridge-head positions were synthesized. These species show a very different ability with regard to the formation of coordination compounds. Whereas compound 1 with the short (C2H4)2O ether units shows no ability to act as a ligand, the compound with the longer (C2H4O)2C2H4 chains between the siloxane fragments could be obtained as the free ligand and with incorporated Li2I2 and Ag2I2 units. The observed coordination modi of the lithium and silver ions in these complexes corresponds to the HSAB- or Pearson concept. The silver ions prefer the soft phosphorus atoms as a bonding partner, while, for lithium, coordination by the hard oxygen atoms is favoured.Empty and filled hybrid cage compounds with siloxane as well as ether units between four phosphorus bridge-head atoms were obtained from the deprotonation of the cyclic siloxadiphosphane [O(SiiPr2)2PH]2 and subsequent reaction with diiodo ethers. These compounds show very different coordination behaviour depending on the length of the ether chain and the metal cation used.
The known MOF UiO-67 of general formula [Zr6O4(OH)4(bpdc)6] [bpdc = biphenyldicarboxylate, O2C(C6H4)2CO2] has been synthesized on a 3 g scale and characterized by BET, TGA, XRD, IR and 13C NMR spectroscopy, and elemental analyses. The chemical accessibility of the hydroxy ligand Zr3(?-OH) was assessed by the addition of D2O: The expected isotopic shift of ?(OH) = 3673 cm–1 to ?(OD) = 2709 cm–1 in the IR spectrum was observed. The OH content in bulk UiO-67, previously mildly activated at 120 °C under vacuum (10–5 Torr) overnight, was quantitatively determined by three methods: (1) By integration of the IR ?(OH) region and comparison with calibrated spectra of MCM-41 previously dehydroxylated at 500 °C, which gave a spectroscopically measured OH content in bulk UiO-67 of 2.2 mmol/g (37 mg?OH/g); (2) by extrapolation of the OH content from the measured weight loss between 250 and 400 °C in TGA, which corresponded to 1.6 mmol?OH/g (27 mg?OH/g); and (3) by chemical titration of UiO-67 with CH3MgBr and GC determination of the evolved methane, which gave 1.8 mmol?OH/g (31 mg?OH/g). The three methods, and in particular the latter chemical titration, are in very good to excellent agreement with the nominal OH content based on the molecular formula [Zr6O4(OH)4(bpdc)6] (expected: 1.9 mmol?OH/g, 32 mg?OH/g; experimental/calculated OH content = 110, 85, and 95?%, respectively, for the three methods). The weak acidity of the OH moiety in UiO-67 was assessed by IR and 31P NMR monitoring of the physisorption of PMe3 in the UiO-67 cavities. Inclusion of the organometallic AuI complex [AuMe(PMe3)] in a 1:1 molar ratio with respect to [Zr6O4(OH)4(bpdc)6] was achieved. Some chemisorption at 20?% of the cornerstone hydroxy sites also occurred to yield [Zr6O4(OH)3(bpdc)6(OAuPMe3)].Thermally stable MOF UiO-67, [Zr6O4(OH)4(bpdc)6], is well-behaved chemically in the bulk: Cornerstone (?3-OH) hydroxy groups react quantitatively with MeMgBr with stoichiometric release of methane. Post-synthetic modification with [AuMe(PMe3)] results in partial covalent grafting of the AuI center onto the cornerstone hydroxy groups.
The syntheses of new potentially tetradentate ligands of the type RN(CH2CMe2OH)2 (1, R = Me2NCH2CH2; 2, R = MeOCH2CH2), their tin(II) derivatives RN(CH2CMe2O)2Sn (3, R = Me2NCH2CH2; 4, R = MeOCH2CH2), the pentacarbonyltungsten complexes RN(CH2CMe2O)2SnW(CO)5 (5, R = Me2NCH2CH2; 6, R = MeOCH2CH2) and their oxidation products with bromine, RN(CH2CMe2O)2SnBr2 (7, R = Me2NCH2CH2; 8, R = MeOCH2CH2), are reported. The compounds were characterized by multinuclear NMR spectroscopy, elemental analysis, electrospray ionization mass spectrometry and single-crystal X-ray diffraction analysis. DFT calculations on compounds 3, 7 and 8 suggest the preference of dimeric over monomeric structures.From dimers to monomers by oxidative addition: The alkoxido-bridged dimeric tin(II) compound 3 undergoes oxidative addition by the reaction with bromine to give compound 7 that in turn is monomeric by an additional intramolecular N?Sn interaction. The methoxy-substituted analogue 8, however, is a dimer.
(4S)-2-(4-Isopropyl-4,5-dihydrooxazol-2-yl)-4-nitrobenzenethiol {(S)-TS} and its tert-butyl derivative {(S)-TS?} were developed as chiral auxiliaries for the asymmetric synthesis of polypyridyl ruthenium complexes. In their deprotonated form, these (mercaptophenyl)oxazolines were used as bidentate ligands and allowed the efficient transfer of chirality from the oxazoline moiety to the ruthenium stereocenter. After the induction of the absolute metal-centered configuration, the auxiliaries were labilized by converting the coordinated thiolate into a thioether ligand upon methylation with Meerwein salt, followed by the thermal replacement with 2,2?-bipyridine or 1,10-phenanthroline ligands under retention of configuration to afford octahedral polypyridyl ruthenium complexes with high enantiomeric excesses. These thiol-based auxiliaries complement our previously developed acid-labile chiral auxiliaries and thus expand the toolbox for the asymmetric synthesis of chiral ruthenium complexes.(Mercaptophenyl)oxazolines were used as chiral auxiliaries for the asymmetric synthesis of polypyridyl ruthenium complexes. Key step was the conversion of a coordinated thiolate into a labilized thioether upon methylation with Meerwein salt, followed by a thermal substitution with an achiral ligand under retention of configuration.
NN–PtII–bis(acetylide) complexes [NN = 4,4?-bis(tert-butyl-2,2?-bipyridine) (dbbpy)] with ethynylpyrene (Pt-2) or 4-ethynyl-1,8-naphthalimide ligands (Pt-3) that show long-lived 3IL triplet excited states (?T = 118.0 ?s) were used as new triplet sensitizers for triplet–triplet annihilation (TTA) based upconversion (UC). UC quantum yields of up to 18.1?% were observed. We found that the triplet–triplet energy-transfer (TTET) processes, which are crucial for the TTA UC, were improved by up to 150-fold and 250-fold with Pt-2 (Stern–Volmer quenching constant KSV = 5.70?×?105M–1) and Pt-3 (KSV = 9.64?×?105M–1), respectively, relative to the model complex dbbpy–PtII–bis(phenylacetylide) (Pt-1) (KSV = 3.80?×?103M–1). The efficient upconversion is attributed to the long-lived triplet excited states as well as the high T1-state energy level of the sensitizers Pt-2 and Pt-3.NN–PtII–bis(acetylide) complexes [NN = 4,4?-bis(tert-butyl-2,2?-bipyridine)] that show long-lived 3IL triplet excited states (?T = 118.0 ?s) were used as new triplet sensitizers for triplet–triplet annihilation (TTA) based upconversion (UC). An UC quantum yield of up to 18.1?% was observed. The triplet–triplet energy-transfer process was improved by up to 250-fold relative to that of the model complex.
The field of biomedical metallodendrimers is an emerging discipline that is attracting prolific attention. Metallodendrimers, like their organic counterparts, are known for their multivalency (high concentration of peripheral end-groups), well-defined architectures and narrow polydispersity. These are characteristics that make metallodendrimers well-suited as innovative scaffolds for the development of new therapeutic agents. Coupled with the surge of interest in the use of various metal complexes to treat various diseases, the application of metallodendrimers in medicinal chemistry is an attractive strategy for therapies involving macromolecules and the advancement of new metal-based therapeutics. In this review, we describe the progress made in the application of metallodendrimers as scaffolds for drug delivery, as metal-based drugs in their own right, and as agents for biosensing, photothermal and photodynamic therapy.The use of metallodendrimers is fast becoming an attractive strategy in the design of a new class of metal-based biomolecules. This review surveys illustrative examples of these multivalent biologically active molecules as metal-based drugs and as agents for biosensing, photothermal and photodynamic therapy.
Silylated N,N?;N?,N??-diborylene-3,4,9,10-tetraaminoperylenes (DIBOTAPs, compounds 1–4) were synthesized by treating 4,9-diaminoperylenequinone-3,10-diimine (DPDI, 1 equiv.) with BH3–THF (2 equiv.), lithiation with n-butyllithium (4 equiv.), and subsequent addition of the corresponding silyl chloride (4 equiv.). The structures of all compounds were determined by single-crystal X-ray diffraction analysis. In all cases, the perylene backbones are not completely planar. In general, local deviations from planarity are smallest within the central C6 ring [root-mean-square deviations (rmsd) range from 0.002 Å for 4 to 0.027 Å for 2·C6D6] and largest within the C3N2B rings [rmsd range from 0.05 Å for 4 to 0.096 Å for 2·C6D6]. The emission spectra of the DIBOTAP derivatives 1–4 in hexane as well as in THF are mirror images of the absorption spectra with Stokes shifts of about 10 nm. By variation of the steric demand of the silyl groups, the luminescence quantum yields could be further influenced. The exchange of all three methyl groups with ethyl (compound 1) or isopropyl (compound 2) substituents resulted in a significant increase in quantum yields with values of 92?% and 89?%, respectively. The observed fluorescence decay is monoexponential for all dyes with typical lifetimes of 5.5–6.6 ns.Silylated N,N?,N?,N??-diborylene-3,4,9,10-tetraaminoperylene are a readily accessible new class of functional dyes. By variation of the steric demand of the N-silyl groups, luminescence quantum yields of up to 92?% were determined.
Two template-induced supramolecular isomers [Pb(2,3-pyde)]n (1 and 2; 2,3-pyde = pyridine-2,3-dicarboxylate) have been synthesized under hydrothermal conditions. Complex 1 displays a 2D network with a point symbol of (42·64)2, whereas complex 2 exhibits a 3D framework with a point symbol of (46·64)2. The study of the stability of the isomers demonstrates that they have high thermal stability and excellent chemical resistance to boiling water and common organic solvents. Interestingly, the two polymers evidently possess different fluorescent properties although they have the same chemical component.Two unique PbII structural isomers [Pb(2,3-pyde)]n (1 and 2; 2,3-pyde = pyridine-2,3-dicarboxylate) have been synthesized by template-induced self-assembly. Complex 1 displays a 2D network, whereas complex 2 exhibits a 3D framework. Interestingly, the two isomers have similar high thermal and chemical stability but possess different fluorescent properties.
Well-defined (?-diketiminate)calcium and -strontium cationic complexes paired with weakly coordinating anions have been prepared in high yields by straightforward protocols. These highly electrophilic species are efficient catalysts for the immortal ring-opening polymerization of lactide and display unusual reactivity by providing a unique example of oxidation of a {BDIiPr} core to give a diiminoalkoxide.Well-defined (?-diketiminato)calcium and -strontium cationic complexes are highly electrophilic species that efficiently catalyze the immortal ring-opening polymerization of lactide and display unusual reactivity by providing a unique example of oxidation of a {BDIiPr} core to give a diiminoalkoxide.
Porous, organically modified silica-based mixed oxides were prepared in a two-step process. First, a mixture of tetraethoxysilane, bis(triethoxysilyl)dipropylamine and, optionally, 1,4-bis(triethoxysilyl)benzene was treated with metal chlorides (ZrCl4, TiCl4, or AlCl3), and no water or water-based catalyst was added to the sols. After film formation, the materials were exposed to ambient humidity to achieve hydrolytic condensation of residual groups. Materials with wormhole-like ordered porosity and uniform mesopores were obtained with metal proportions up to about 20?%. According to XPS measurements, the metals are homogenously distributed in the silica matrix.Porous, organically modified silica-based mixed oxides were prepared by sol-gel processing of organotrialkoxysilanes with bridging amono groups and metal chlorides. Materials with ordered porosity and uniform mesopores were obtained with metal proportions up to about 20?%.
(Trimethylsilyl)methylrubidium [RbCH2SiMe3] (1) and (trimethylsilyl)methylcesium [CsCH2SiMe3] (2) were prepared by metathesis reactions of (trimethylsilyl)methyllithium [LiCH2SiMe3] with rubidium or cesium tert-butoxide in n-hexane. Both new compounds are pyrophoric powders which were characterised by NMR spectroscopy and elemental analyses. They can be used as deprotonating agents towards secondary amines such as 2,2,6,6-tetramethylpiperidine (TMPH). The resulting amides [RbTMP] (3) and [CsTMP] (4) form temperature-sensitive, n-hexane-insoluble orange solids. Treatment with the bidentate donor N,N,N?,N?-tetramethylethylenediamine (TMEDA) produces the corresponding n-hexane-soluble complexes. The crystal structures of [(TMEDA)RbTMP] (3a) and [(TMEDA)CsTMP] (4a) were determined to be closely related to that of [(TMEDA)KTMP]. Thus they are dimers with frameworks that consist of four-membered M–N–M–N rings (M = Rb, Cs or K, N = TMP). The versatility and stability observed should make these (trimethylsilyl)methyl and TMP compounds of rubidium (1, 3a) and cesium (2, 4a) valuable starting points for further exploration of the chemistry of these heavy alkali metals.The synthesis of (trimethylsilyl)methyl-rubidium [RbCH2SiMe3] and -cesium [CsCH2SiMe3] is reported, which were then used to form the corresponding 2,2,6,6-tetramethylpiperidides by treatment with the appropriate amine. These rubidium and cesium amides were isolated as TMEDA-solvated dimers [(TMEDA)RbTMP]2 and [(TMEDA)CsTMP]2 whose frameworks consist of four-membered M–N–M–N rings.
Exchange reactions of 2,2-dimethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselena-2-silacyclopentane with phosphorus trihalides PX3 (X = Cl, Br, I) led to the corresponding phospholanes in high yield. The solid-state structure of the iodide was determined by X-ray crystallography. Treatment of the bromide with nBu3SnH afforded the parent phosphane. The reaction of the iodide with LiAlH4 in [D8]toluene proceeded very slowly and mainly gave the deuterated phosphane. All products were characterised in solution by multinuclear magnetic resonance methods (1H, 13C, 31P and 77Se NMR). Molecular gas-phase geometries were optimised at the B3LYP/6-311+G(d,p) level of theory, and NMR parameters were calculated.Cleavage of Si–Se bonds with PCl3, PBr3 or PI3 affords the corresponding 1,3,2-diselenaphospholanes in high yield, and the bromide and iodide could be converted into the parent phosphane. 1H, 13C, 31P and 77Se NMR spectroscopy in solution, an X-ray structural analysis of the iodide and calculations of NMR parameters by using DFT hybrid methods [RB3LYP/6-311+G(d.p) level] complete the characterisation.
Mono-, di- and tetraanions of rubrene, (C42H28, Rub0), were generated by the controlled reduction of neutral polyarene with various alkali metals in the appropriate solvent. The X-ray diffraction studies of the resulting adducts of Rub1–, Rub2– and Rub4– with alkali-metal ions revealed the distortion of the rubrene core upon the stepwise acquisition of electrons. Coordination of the Cs+ ion and a noticeable deformation of Rub1– are observed at the first reduction step. Two types of rubrene dianions showing an essentially different conformation and coordination environment for the central tetracene core have been seen in the cesium adduct of Rub2–. Various types of supramolecular assembly between the tetrareduced rubrene anion, Rub4–, and lithium or rubidium cations have been found in the corresponding products in the solid state. The structures of rubrene anions and their aggregation with alkali-metal ions in solution have been studied by ESR and multinuclear NMR (1H, 13C, 7Li and 133Cs) spectroscopy.Mono-, di- and tetraanions of rubrene have been prepared by a stepwise alkali-metal reduction. The geometries of charged rubrene anions and their supramolecular aggregation with alkali-metal ions in the solid state and solution are discussed based on single-crystal X-ray diffraction studies, ESR and multinuclear NMR spectroscopy.
Eight 5-aminotetrazolate (AT) salts based on the 1,2,3-trimethylimidazolium (1), 1,3-dimethylimidazolium (2), 1-ethyl-3-methylimidazolium (3), 1-butyl-3-methylimidazolium (4), 1-isobutyl-3-methylimidazolium (5), 1-(3?-methylbutyl)-3-methylimidazolium (6), 1-hexyl-3-methylimidazolium (7) and 1-methyl-3-octylimidazolium (8) cations have been synthesized in high yields and fully characterized by IR and NMR spectroscopy and elemental analysis. White plate crystals of 1 were isolated in methanol/diethyl ether and crystallized. Both the AT anion and the 1,2,3-trimethylimidazolium cation in 1 were delocalized. Differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests were used to assess the thermal stabilities of the AT salts. These salts decomposed within the temperature range 230 °C–262 °C. Salts 3–8 are very fluent room-temperature ionic liquids, whose glass transition temperatures are low. Their viscosities at 30 °C are in the range from 92 cP to 208 cP. A correlation between the viscosity and temperature was found, and the ionic liquids to do not display an Arrhenius temperature behaviour. In addition, the standard enthalpies of formation of salts 1–8 were investigated and analyzed by the theoretical methods. Salt 2 with the 1,3-dimethylimidazolium cation gave the highest positive enthalpy of formation. For the assessment of the energetic character of the AT salts, impact sensitivities and friction sensitivities were recorded. These AT salts are insensitive to impact (>40 J) and friction (>360 N) confirmed by UN standards. The reactions of these AT salts with 100?% HNO3 were also determined.5-Aminotetrazolate is a good anion to construct low-viscous and low-melting room-temperature ionic liquids (3–8). Its delocalized tetrazolate ring facilitates the decrease in the Coulomb interactions. 5-Aminotetrazolate-based ionic liquids are potential liquid materials with high heats of formation and low sensitivity to heat, shock and friction.
Cobalt(II) iodide, bromide, and chloride react with 1 equiv. of IPr [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene] to form a series of tetrahedral dimeric (30e) complexes of cobalt(II) in good yields. These were transformed into the monomeric forms in the presence of pyridine. These complexes were characterized by SQUID, XPS, UV/Vis spectroscopy, elemental analysis, and X-ray crystallography, and were found to have high catalytic activity for Kumada–Tamao–Corriu cross-coupling reactions of aryl halides.A series of cobalt(II) dimeric tetrahedral (30e) complexes were obtained in goodyields and were transformed into the monomeric forms with pyridine. These complexes were characterized by SQUID, XPS, UV/Vis spectroscopy, elemental analysis, and X-ray crystallography, and were found to have high catalytic activity for Kumada–Tamao–Corriu cross-coupling reactions of aryl halides.
A new open-framework manganese borophosphate, KMnBP2O7(OH)2, has been prepared under ionothermal conditions in the ionic liquid 1-butyl-1-methylpyrrolidinium bromide. Single-crystal X-ray diffraction analysis showed that KMnBP2O7(OH)2 [monoclinic, P21/c, a = 6.659(1), b = 12.049(2), c = 9.790(2) Å, ? = 109.12(3)°, V = 742.2(3) Å3, and Z = 4] has an unprecedented open-framework structure. {MnO5(OH)} octahedra and {BO3(OH)} and {PO3(OH)}/{PO4} tetrahedra link to form a 3D framework with distorted eight-membered-ring channels along the crystallographic [001] direction. The negative charges of the inorganic framework are balanced by K+ ions located in the channels. At room temperature, KMnBP2O7(OH)2 shows a bright orange-red luminescence that redshifts with decreasing temperature. The luminescence lifetimes were determined to be 0.17 ms at room temperature and 3.49 ms at 77 K. Below 3 K, d5 Mn2+ of two neighboring, edge-sharing {MnO5OH}2 units couple antiferromagnetically, and the magnetic state can be best described as a singlet spin system. These singlets continuously turn into triplets when increasing the magnetic field up to 7 T at 2 K due to relatively weak spin–spin coupling through two identical 98.92(6)° Mn–O–Mn superexchange paths, turning the system into a metastable ferromagnetic state.A new open-framework manganese borophosphate, KMnBP2O7(OH)2, has been prepared under ionothermal conditions with the help of an ionic liquid. It shows bright orange-red luminescence and features interesting magnetic properties.
The syntheses of six new mixed P/S-donor two-coordinate AuI complexes are described. The complexes incorporate a pteridinyl ligand coordinated through a thiolate donor, and an ancillary tertiary phosphane (PPh3 or PCy3). The mercapto-pteridine ligands (L1–L3) differ in the nature of the substituents on the pteridine core. An X-ray crystal structure was obtained for one of the examples, [(L1)Au(PPh3)], revealing weak intermolecular interactions between two molecules of the complex: ?–? contacts between aromatic rings appear to support an intermolecular Au–Au contact of approximately 3.05 Å. All of the complexes are luminescent in solution, with emission arising from tuneable ligand-based excited states, and characterised as a perturbed fluorescence in nature. In this context, complexes of L3 displayed useful visible absorption and emission. Preliminary cytotoxicity assessments were conducted using the MTT assay, and the complexes each displayed impressive anti-proliferative activities (IC50 < 5 ?M) with respect to four different adenocarcinoma cell lines (MCF7, A549, PC3 and LOVO). For a given pteridine moiety, triphenylphosphane appeared to be the co-ligand of choice for enhancing biological activity.The syntheses and characterisation of neutral, two-coordinate AuI complexes incorporating a thiol-derived pteridine unit are described. The complexes possess luminescence arising from ligand-centred excited states. All of the complexes display notable anti-proliferative activities (IC50 < 5 ?M) with respect to four different adenocarcinoma cell lines.
The synthesis of 3-substituted indoles was investigated through a multicomponent reaction (MCR) approach by using aldehydes, indole and malononitrile as the reagents. The reaction was catalyzed by Lewis acidic Zn(salphen) complexes and their performance was compared with a number of other ZnII structures and M(salphen)s, which showed the Zn(salphen)s to be superior. However, the complex nature of this three-component reaction (3-CR) results in substantial byproduct formation that arises from the intermediate benzylidene malononitrile species. The 3-CR was studied in detail that covered the influence of the base, solvent, reagent stoichiometry and also involved stability studies. The results led to a mechanistic proposal in which the benzylidene malononitrile intermediate plays a central role; it is one of the major species that is formed in most of the catalytic reactions studied. Furthermore, it provided a prelude for the in situ reaction with the malononitrile reagent, which most probably affords a complex mixture of N-containing heterocycles.The Zn(salphen)-mediated synthesis of 3-substituted indoles by using a multicomponent reaction approach is reported. The reaction parameters were investigated and the selectivity for the 3-CR product was examined under various conditions. Selectivity for the target compound is significantly compromised by side-product formation due to in situ reaction of the intermediate species with malononitrile, which affords N-heterocyclic structures.
A series of ammonium–carboxylate and ammonium–sulfonate betaines was synthesized and studied by single-crystal X-ray diffraction analysis to investigate the weak intermolecular interactions as well as the intramolecular interactions in the solid state. None of the expected intramolecular anion–? interactions could be observed, probably because of the steric demands and the reduced nucleophilicity of the anionic part of the betaines. Nevertheless, a weak intermolecular anion–? interaction between the anionic part of the betaine and the pentafluorophenyl unit is present in the structure of 5a.A series of betaines bearing pentafluorobenzyl groups was synthesized and investigated with respect to intra- and intermolecular interactions in the solid state. The carboxylic end of betaine 5a interacts with the electron-deficient arene of a neighbouring molecule in the solid phase.
The complexes [Na{HC(PPh2S)2}] (Na3a), [Na{HC(PPh2Se)2}] (Na3b), [K{HC(PPh2S)2}]? (K3a), [K{HC(PPh2Se)2}]? (K3b), [Mg{HC(PPh2S)2}2] (Mg(3a)2), [Mg{HC(PPh2Se)2}2] (Mg(3b)2), and [Zn{HC(PPh2S)2}2] [Zn(3a)2] have been prepared in good yields (69–92?%) by treatment of the neutral ligands H2C(PPh2E)2 (1a, E = S; 1b, E = Se) with [Na{N(SiMe3)2}] (Na3a), NaNH2 (Na3b), [K{N(SiMe3)2}] (K3a and K3b), [Mg{N(SiMe3)2}2] [Mg(3a)2 and Mg(3b)2], or Me2Zn [Zn(3a)2] as base in THF/toluene. These compounds were characterized in solution by multinuclear (1H, 13C, 31P, and 77Se) NMR spectroscopy and the X-ray structures of K3a, K3b, Mg(3a)2, Mg(3b)2, and Zn(3a)2 were determined. In the solid state, the E,E?-chelated ligands in K3a and K3b also engage in potassium–chalcogen interactions with adjacent molecules to form one-dimensional ladder structures. With K3a, both sulfur atoms of the ligand are involved in chelation leading to four-membered K2S2 rings, whereas only one selenium atom is tricoordinated in K3b; significant potassium···aryl interactions are also observed in both structures. In the homoleptic magnesium complexes Mg(3a)2 and Mg(3b)2, the E,E? chelation by the methanide ligands is supplemented by weak, unequal Mg···C interactions [2.781(10) and 3.199(7) Å for Mg(3a)2; 3.331(8) and 3.217(7) Å for Mg(3b)2]. The zinc complex Zn(3a)2 is isostructural with the previously reported selenium analogue Zn(3b)2. The X-ray structures of the S,S?-chelated complex [(TMEDA)Li3a] as well as new polymorphs of 1a and 1b are also reported.Bis(chalcogenophosphinoyl)methanide complexes of Na, K, Mg, and Zn have been synthesized by reaction of neutral ligands H2C(PPh2E)2 (E = S, Se) with an appropriate base. The K complexes form one-dimensional polymeric structures through K···E interactions between adjacent molecules. E,E? chelation of the methanide ligand in Mg[HC(PPh2E)2]2 is supplemented by weak, unequal Mg···C interactions.
The results of studies focussed on copper complexes of a variety of ligands with an NN4 donor set are reported. The permethylated tetrapodal ligand 2 forms a complex with copper(I) which, upon reaction with dioxygen at –90 °C, yields a product having a bis(?-oxido)dicopper(III) core (“O-type” product, 10), as inferred from UV/Vis and resonance-Raman spectroscopic data. The UV/Vis spectrum of 10 has two bands at 300 and 404 nm, with extinction coefficients of 9400 and 10400 L?mol–1?cm–1, respectively. Resonance-Raman spectra display two 16O/18O-sensitive bands which, based on the isotopic shifts and the absolute frequencies, are attributed to the Cu–O stretching modes of the O-type product. Complex 10 shows tyrosinase-like activity, as its reaction with sodium p-tert-butylphenolate at –90 °C in THF yields p-tert-butylcatechol, in an ortho-hydroxylation reaction (yield: 30?%). Two new rigid tetrapodal pentadentate ligands (the “superpods” 3 and 4) can be synthesized by condensation of the primary polyamine 1 with paraformaldehyde. Their copper(II) complexes (5 and 6) have been spectroscopically characterized. As ascertained by X-ray crystallography, 5 has the CuII ion in a tetragonal-pyramidal environment, with almost uniform Cu–N bond lengths (basal bonds: 2.052 Å and 2.070 Å; apical bond: 2.077 Å). No significant Jahn–Teller distortion is observed here. In 6, the ligand acts as a multinucleating donor, which leads to the formation of a ladder-like cluster of [Cu(?3-OH)] units containing a total of two ligands, six copper(II) ions, four hydroxido ligands and eight trifluoroacetate ions. Two of the trifluoroacetate ions are non-coordinating. Variable-temperature magnetic susceptibility data are reported for this hexanuclear copper(II) cluster. Copper(I) complexes of 1 and 3 have been characterized and allowed to react with molecular oxygen, which caused the decomposition of the complexes. The IR spectra of the oxygenation products have bands at 1652 and 1632 cm–1, respectively, which are absent in the spectra of 1 and 3, suggesting that amine functions have been oxidized to imines.Copper(I/II) complexes of varying nuclearity have been obtained with a series of tetrapodal pentadentate N-donor ligands.
The trapping of nanoparticles inside a hybrid matrix is of great importance for the design of flexible devices with good mechanical properties and for the manipulation of nanoparticles whilst avoiding the use of nanopowders. In this work, transparent coloured coatings on glass were prepared by incorporating Goethite nanorods in a silica:PHEMA [poly(hydroxyethyl methacrylate)] hybrid matrix. Results show that incorporation of Goethite with a volume content higher than 27?% leads to the formation of a porous structure through a phase separation mechanism which induces a dramatic collapse of the mechanical properties. When the Goethite volume content is below 16?%, the mechanical properties of the coating are governed by the interactions between organic and inorganic domains. Goethite interacts preferentially with the silica network through the formation of hydrogen bonds and no direct interactions with PHEMA were observed. In the absence of strong covalent bonds between the silica:PHEMA hybrid and the nanoparticles, Goethite nanorods do not provide any mechanical strengthening. As a result, interpenetration between silica and PHEMA networks enables fine tuning of the final mechanical properties with the coating silica content.The incorporation of Goethite nanoparticles in a hybrid PHEMA:SiO2 matrix allows the elaboration of coloured coating on glasses without changing the mechanical or optical properties of the layer. Beyond a nanoparticle content of 25?vol.-%, a significant phase separation occurs which increases the porosity of hybrid matrix making it less reinforced and the layer becomes opaque.
A new scorpionate ligand, Na[HB(mim)2(PntBu)] (Na[PnBm]), with one pyridazinyl-3-thione and two methimazolyl (mim) substituents was prepared by mixing 6-tert-butylpyridazine-3-thione (HPntBu) and sodium dihydridobis(methimazolyl)borate (Na[Bm]) in boiling xylene. Addition of CuCl to a solution of Na[PnBm] in methanol in the presence of PR3 gave the monomeric copper(I) complexes [Cu{PnBm}(PR3)] (R = cyclohexyl 1, phenyl 2) in good yields. They were characterized by NMR spectroscopy and in the case of 2 also by single-crystal X-ray diffraction analysis. The latter revealed a compound in which the ligand is coordinated in a ?3-S,S,H fashion, exhibiting a 3-center-2-electron B–H···Cu interaction. Reaction of the ligand Na[PnBm] with CuCl in the absence of phosphane yielded a copper(I) complex, which was determined to be [Cu{PnBm}] (3). Variable-temperature 1H NMR spectroscopy points to the occurrence of two dimeric isomers in solution, which interconvert in a fluxional behavior at room temperature. DFT calculations show that two isomers with a ?3-Smim,Smim,H or a ?3-Hmim,SPn,H coordination mode have very similar energies with a low energy barrier (25.4 kJ/mol) for their interconversion.A new hybrid scorpionate ligand, Na[HB(mim)2(PntBu)] (Na[PnBm]), containing the methimazole and pyridazine moieties was prepared. Reaction of the ligand with CuCl and phosphane donors gave complexes [Cu{PnBm}(PR3)] (R = cyclohexyl 1, phenyl 2), whereas without phosphane donors dimeric complex [Cu{PnBm}]2 (3) was formed. The fluxional behavior was further investigated by theoretical calculations.
The reaction of the C-functionalized cyclam chelating agent 1,4,8,11-tetraazacyclotetradecane-6-carboxylic acid (1) with CuCl2 generated a stable and neutral complex 2, which was characterized by elemental analysis, IR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), EPR spectroscopy and X-ray crystallography. The secondary amine groups of 1 were protected to generate 3, which was further conjugated with the bombesin (BN) derivative H2N-(Ornithine)3-BN(2–14) by a solid phase peptide synthesis method. After cleavage from the resin and deprotection, the resulting product 5 was obtained and characterized with ESI-MS and NMR spectroscopy, and was subsequently complexed under mild conditions with CuCl2 to generate complex 6 in high yield. Complex 6 was characterized with UV/Vis spectroscopy, ESI-MS and EPR spectroscopy. The stability of complexes 2 and 6 was tested against cysteine, histidine and glutathione, and both complexes were found to be stable. The cyclam BN conjugate 5 and its CuII complex 6 were suitable for targeting the gastrin releasing peptide receptors (GRPrs) that are over expressed on PC-3 cells. Both 5 and 6 showed high binding affinity to GRPrs during in vitro cell assays with human PC-3 prostate cancer cells. The half maximal inhibitory concentration (IC50) values observed for 5 and 6 (0.30?±?0.03 and 0.33?±?0.03 nM, respectively) were similar to that of the [Tyr]4-BN peptide (0.45?±?0.04 nM), which was used as standard.A new bombesin copper complex based on a bifunctional cyclam derivative was synthesized, characterized, and evaluated for its binding affinity to bombesin receptors through in vitro cell assays with PC-3 cells.
Three new dinuclear NiII complexes, [Ni2L2(NO3)2] (1), [Ni2L2(NO2)2] (2), and [Ni2L2(CH3COO)2(H2O)] (3), have been synthesized by using a tridentate Schiff base ligand, 2-({[3-(dimethylamino)propyl]imino}methyl)phenol (HL), along with a nitrate, nitrite, or acetate ion, respectively, as co-ligand. These three complexes were characterized by spectral analysis, X-ray crystallography, and variable-temperature magnetic susceptibility measurements. The structural analyses revealed that the NiII ions are coordinated by the deprotonated chelating tridentate Schiff base and possess a distorted octahedral geometry in all three complexes. Complexes 1 and 2 are two di-?2-phenoxido-bridged species in which the nitrate and nitrite act as chelating co-ligands. However, in complex 3, in which the acetate anion is monodentate, an additional water bridge is present along with two ?2-phenoxido bridges making the complex a face-sharing bi-octahedron. Magnetic susceptibility measurements indicate an antiferromagnetic intradimer interaction in complexes 1 and 2 with J values of –20.34(5) and –25.25(4) cm–1, respectively, whereas complex 3 shows a dominant ferromagnetic exchange coupling with J = 19.11(9) cm–1. DFT calculations were performed, and the theoretically obtained J values of –19.99 (for 1), –24.19 (for 2) and 18.81 cm–1 (for 3) corroborate very well the experimental results. An attempt has also been made to correlate the effect of Ni···Ni distances and bridging Ni–O–Ni angles on the coupling constants of the NiII complexes through DFT calculations. The relative energy calculations show that the diphenoxido-bridged complexes are stable at larger bridging angles, and consequently the coupling is antiferromagnetic, whereas with an additional water bridge, the formation of complexes with the Ni–O–Ni bridging angle in the ferromagnetic region is energetically profitable.Of the three dinuclear NiII complexes synthesized, the two double-phenoxido-bridged complexes are antiferromagnetically coupled, whereas the third with an additional water bridge is ferromagnetic. A theoretical study has been performed to show the influence of the Ni–O–Ni bond angle on the exchange coupling constants.
The silver chloride and gold chloride complex of the extremely sterically shielding N-heterocyclic carbene ligand IPr** have been synthesized and characterized. Formally, eight methyl groups of IPr have been replaced by 4-tert-butylphenyl substituents, and two para-methyl groups have been added. The world record for the ligand's buried volume (55.4?% for IPr**AuCl, and 56.7?% for IPr**AgCl) has been determined by single-crystal X-ray analyses. Reaction of IPr**AuCl with AgSbF6 in toluene yields AgCl and a cationic gold complex with toluene coordination. The same reaction in 1,2-dichloroethane leads to precipitation of AgCl and an equilibrium of [IPr**Au]SbF6 and [IPr**AuClAg]SbF6. Single crystals of the latter were suitable for an X-ray structure analysis, which reveal an Au–Cl–Ag triangle with an almost undisturbed IPr**–Au–Cl fragment and the coordination of two IPr** arenes to a silver cation. The structural parameters emphasize the role of NHC-Au cations as highly electrophilic “soft protons”.The reaction of AgSbF6 with the gold chloride complex of the extremely bulky N-heterocyclic carbene ligand IPr** (simplified in the figure) revealed a silver cation coordinated to a single AuCl fragment – an intermediate proposed for most gold-catalyzed organic transformations.
In this contribution, we report the first hard-X-ray-induced thermal hysteresis (HAXITH). The bistability in [Fe(phen)2(SCN)2] (phen = 1,10-phenanthroline) is proven by alternately heating and cooling the sample under permanent irradiation with hard X-rays. Within the hysteresis a serpentine-like switching effect is observed. HAXITH is a new tool to monitor cooperativity among the switching units. It exhibits a threshold similar to that observed with visible light excitations.We introduce the first hard-X-ray-induced thermal hysteresis (HAXITH). This bistability is observed by heating and cooling cycles of the sample under permanent irradiation with hard-X-rays. Within the hysteresis a serpentine-like switching effect is observed. HAXITH is a new tool to observe cooperativity among the switching units.
Six dinuclear complexes, [Ln2(hfac)6(H2O)2(L)] [Ln = Y (1) and Er (2)], [Yb2(hfac)6(L)] (3), [Ln2(tta)6(L)]·3CH2Cl2 [Ln = Y (4) and Er (5)] and [Yb2(tta)6(L)]·2C6H14 (6), have been prepared by coordination reactions between the [Ln(?-diketonate)3]·2H2O (Ln = YIII, ErIII and YbIII; ?-diketonate = hfac– or tta–) building blocks and 4,4?,7,7?-tetra-tert-butyl-2,2?-bi-1,3-benzodithiole-5,5?,6,6?-tetrone ligand (L), which acts as a bridge between the two metal centres. Their X-ray structures reveal that the symmetries around the lanthanide atoms depend on the ?-diketonate anions and the size of the 4f ions. The dc magnetic measurements showed paramagnetic behaviour with thermal variations of the ?MT products that depend on the crystal-field symmetry around the 4f ions. The photophysical properties of the coordination complexes were studied by solid-state absorption spectroscopy, and DFT calculations were carried out on the free ligand L and the diamagnetic YIII derivatives 1 and 4. Irradiation of the charge-transfer (ILCT) band of L [?ex = 700 nm (14285 cm–1)], 1 and 4 [?ex = 750 nm (13335 cm–1)] induced weak fluorescence in L at 12500 cm–1 (for free L) and in 1 at 12200 cm–1, whereas in the case of 3, irradiation at 13335 cm–1 induced weak line-shape emission assigned to the 2F5/2 ? 2F7/2 (9880 cm–1) ytterbium-centred transition. No residual charge-transfer emission was observed in this last case attesting the efficient energy transfer from the excited charge-transfer state to the 2F5/2 state. The weak intensity of the emissions should mainly be attributed to energy back-transfer between the relaxed CT excited state and the CT state. Nevertheless, sensitisation of the YbIII luminescence in 3 was achieved through the lowest-energy donor excited state (13585 cm–1) reported until now.YbIII luminescence of the paramagnetic dinuclear complex [Yb2(hfac)6(L)] (L = 4,4?,7,7?-tetra-tert-butyl-2,2?-bi-1,3-benzodithiole-5,5?,6,6?-tetrone) is induced by the lowest-energy irradiation (13335 cm–1) for the sensitisation of near-infrared emissive lanthanides.
The role of ligands (i.e. hexadecylamine, dodecylamine, or octylamine associated with oleic acid) on the formation of ZnO nanoparticle superlattice structures (NSSs) was investigated by NMR spectroscopy in C7D8. This full study demonstrates that ion-paired ammonium carboxylates play a crucial role in NSS formation. Using different NMR spectroscopic experiments, such as 1H NMR, pulsed field gradient spin-echo (PGSE) NMR, and NOESY, we evidenced that the introduction of long-alkyl-chain carboxylic acid molecules into a colloidal solution of ZnO nanoparticles (NPs) stabilized by amine ligands leads to rearrangement of the amines on the surface of the NPs with the formation of ammonium carboxylate. This NMR spectroscopic study evidences the dependence of the nature of the ligands adsorbed on the NP surface on the colloid concentration. At high concentration, several ligand shells with a lot of ion-paired ammonium carboxylate and inclusion of amine are observed. At low concentration, the ion-paired ammonium carboxylate shells are replaced by amine shells. This NMR spectroscopic study suggests that the driving force of NSS formation is the presence of ion-paired ammonium carboxylate shells around the nanoparticle.NMR spectroscopic evidence was provided for the role of ion-paired ammonium carboxylate on the formation of nanoparticle superlattice structures (NSSs). The ligand present on the nanoparticle surface was studied as a function of the colloid concentration. The effect of the alkyl chain length of the ligand on NSS formation was investigated.
Vibrational spectroscopy can be used to follow spin transition processes, induced by a change of temperature, pressure, or irradiation with light of suitable wavelength, in spin-crossover (SCO) molecules. In this contribution, recent applications of infrared and Raman spectroscopy, as well as nuclear inelastic scattering (NIS), are reviewed. In the past, vibrational spectroscopic methods have been used to identify spin marker bands that reflect the different spin states in a sample. This application is certainly still one of the major ones and is used especially in connection with mode assignments by modern density functional calculations. However, during the last years also major progress has been achieved (1) in studying nano- and microstructures of SCO complexes, (2) in the search for spin domains, and (3) also in the investigation of the spin switch process itself, which is nowadays studied not only by ultrafast time-dependent UV/Vis spectroscopy, but also by femtosecond IR and Raman spectroscopy.Recent applications of infrared and Raman spectroscopy, as well as nuclear inelastic scattering (NIS), with respect to the study of spin-crossover (SCO) phenomena are reviewed. A special focus lies on micro- and nanostructures of SCO complexes as well as on time-dependent phenomena.
In the pursuit of dual-mode imaging agents of the tumour hypoxia markers carbonic anhydrases (CA) IX and XII, sulfonamides 4-(2-aminoethyl)benzenesulfonamide and 1,3,4-thiadiazole were functionalised with a 4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene (BODIPY) dye to afford fluorescent aromatic sulfonamide conjugates as potential agents for simultaneous positron emission tomography and fluorescence imaging. Both compounds exhibited nanomolar potency as inhibitors of four CA isoforms: the cytosolic CA I and II, and the transmembrane CA IX and XII. Cell uptake experiments with a CA IX positive and null cell line showed no uptake with the 1,3,4-thiadiazole species in either cell line, whilst the benzenesulfonamide species showed uniform internalisation in both cell lines that limited these compounds as selective imaging agents.4,4-Difluoro-4-borata-3a-azonia-4a-aza-s-indacene (BODIPY)-functionalised sulfonamides have been tested for their carbonic anhydrase (CA) selectivity by binding-affinity assays against CA IX and CA XII. In vitro studies in a CA IX transfected cell line have highlighted the importance of both the nature of the fluorophore and the presence of a secondary binding interaction for selective CA inhibition.
New chiral cis-dioxidomolybdenum compounds [MoO2(acac)(RN,O)] [R = Bn (1), pic (2)] and [{MoO2(acac)}2{?-(O,N,N,O)}] (3) have been synthesized by treating [MoO2(acac)2] with the corresponding enantiomerically pure alcohol-imino compounds derived from (+)-?-pinene modification, (RN,OH) (R = Bn, pic) and (HO,N,N,OH), respectively. Compound [MoO2Cl2(O,N,N,O)] (4) has also been prepared. All the compounds were fully characterized both in solution and in the solid state, including by single-crystal X-ray diffraction analysis of enantiomerically pure 3. DFT studies support the stereoselectivity of the synthesis of compound 3. Catalytic olefin epoxidation studies were performed with cis-cyclooctene, (R)-limonene, and trans-?-methylstyrene by using derivatives 1–4 as catalyst precursors and tert-butyl hydroperoxide (TBHP) or H2O2 as oxidant. All the catalytic systems showed high chemoselectivity irrespective of the terminal oxidant used. The molybdenum compounds exhibited medium to high catalytic activity at mild reaction temperatures, but no substantial optical induction was observed. This study represents the first use of chiral monoacetylacetonato-cis-dioxidomolybdenum compounds as homogeneous olefin epoxidation catalysts.Pure chiral cis-dioxidomolybdenum complexes containing alkoxo-imino ligands derived from (+)-?-pinene have been prepared, and their catalytic activity in olefin epoxidation has been evaluated. All new complexes displayed high activity and chemoselectivity with TBHP (tert-butyl hydroperoxide) and H2O2 as oxidants.
An electrochemical technique has been used to synthesize Ni(TCNQF4)2(H2O)2 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane). The method involves the reduction of solid TCNQF4 immobilized on an electrode surface in contact with Ni2+?(aq.)-containing electrolyte. The electrochemically irreversible, but chemically reversible solid–solid TCNQF4/Ni(TCNQF4)2(H2O)2 interconversion process is governed by nucleation and growth kinetics and is represented by the overall reaction: 2TCNQF4?(s, electrode) + Ni2+?(aq.) + 2H2O + 2e [rlhar2] Ni(TCNQF4)2(H2O)2?(s, electrode). Thus, the formation of Ni(TCNQF4)2(H2O)2 involves the one-electron reduction of TCNQF4 to [TCNQF4]·– coupled with an ingress of Ni2+?(aq.) from the aqueous electrolyte, while the reverse scan represents the oxidation of [TCNQF4]·– to TCNQF4 coupled with the egress of Ni2+?(aq.). Cyclic voltammograms for the TCNQF4/Ni(TCNQF4)2(H2O)2 solid–solid phase transformation are independent of the electrode material and the identity of the Ni2+?(aq.) counteranion but are strongly dependent on the concentration of Ni2+?(aq.) and the scan rate. UV/Vis, infrared, and Raman spectra confirm the presence of [TCNQF4]·– in the newly synthesized material. The composition of Ni(TCNQF4)2(H2O)2 was deduced from thermogravimetric and elemental analyses. Scanning electron microscopic images of Ni(TCNQF4)2(H2O)2 electrocrystallized onto the surface of an indium tin oxide electrode show a thin film morphology. Magnetic and conductivity data demonstrate that the complex behaves as a classical paramagnet and is a typical semiconductor with a band gap close to that of an insulator.Ni(TCNQF4)2(H2O)2 was formed by a solid–solid phase transformation with a TCNQF4-modified glassy carbon electrode in aqueous Ni(NO3)2. The transformation is electrochemically irreversible but chemically reversible and is governed by nucleation and growth kinetics. The product is a classical paramagnet and a typical semiconductor with a band gap close to that of an insulator.
Two structurally related tetranuclear complexes, [Ru4(?4-?2C,S-IMe–CS)(?4-S)(?-CO)2(CO)9] (1) and [Ru4(?4-?2C,N-TMe–CNPh)(?4-S)(?-CO)(CO)10] (2), have been isolated from reactions of [Ru3(CO)12] with 1 equiv. of the betaines IMe–CS2 (IMe = 1,3-dimethylimidazol-2-ylidene) and TMe–C(S)NPh (TMe = 3-methylthiazol-2-ylidene), respectively. Both products contain ?4-S ligands that arise from the unprecedented cleavage of the thiocarbonyl C–S bonds of the corresponding betaines. A hexanuclear derivative, [Ru6{?3-?4C2,N,S-S(CH)2N(Me)CCNPh}2(?4-S)2(CO)14] (3), has also been obtained from the reaction involving TMe–C(S)NPh. This product arises not only from the cleavage of the betaine thiocarbonyl C–S bond, but also from the additional activation of the C–S bond within the thiazole ring.The products of the reactions of NHC–C(S)X betaines (NHC = N-heterocyclic carbene; X = S, NPh) with [Ru3(CO)12] contain ?4-sulfido ligands that arise from the cleavage of the betaine thiocarbonyl C–S bond. The additional activation of a ring C–S bond has been observed for a thiazole-derived betaine.
Polycrystalline fine powders of yttrium aluminate doped with Ce3+ were synthesised by spray pyrolysis of a polymeric precursor, which was obtained by dissolving the corresponding nitrates in a solution of ethylenediaminetetraacetic acid (EDTA) in ethylene glycol (EG). Aerosol decomposition was performed at 550 °C followed by an additional thermal treatment (900–1100 °C). The yield of either a single yttrium aluminium perovskite (YAP) phase or a single yttrium aluminium garnet (YAG) phase was investigated as a function of the predefined yttrium/aluminium ratio, the cerium doping concentration, the processing temperature, and the thermal-treatment regime, which included the variation of the heating and cooling rates (dT/dt), the residence time (?), and the atmosphere. Changes in the composition and structure of the precursor during thermal decomposition were investigated by thermogravimetric and differential thermal analysis (TGA/DTA) and FTIR spectroscopy. The particle morphology and structure were analysed by a combination of scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) and by high-resolution transmission electron microscopy (HR-TEM). The structural refinement was based on the phase identification performed by X-ray powder diffraction (XRPD). The emission spectra were recorded within the range 325–800 nm by applying excitation wavelengths of 297 (YAP) and 450 nm (YAG). The employed synthesis conditions assured the formation of spherical, non-agglomerated particles with well-developed surfaces and diameters between 200 and 800 nm. For a predefined Y/Al ratio of 1:1, lower processing temperatures combined with longer heat treatments under stationary conditions resulted in a multiphase system, composed of YAP, YAG, and monoclinic yttrium aluminate (YAM) phases. However, a short heat treatment with a high heating rate (200 °C/min) at higher temperatures results in the formation of a kinetically favoured pure YAP hexagonal phase. On the other hand, for a predefined Y/Al ratio of 3:5, the generation of a thermodynamically favoured pure YAG phase has been confirmed, regardless of the applied heat-treatment conditions. Although incomplete, Ce3+ introduction into the host matrix has been detected by XRPD and luminescence measurements.Highly spherical, non-agglomerated, polycrystalline yttrium aluminium perovskite (YAP) and yttrium aluminium garnet (YAG) particles were synthesised by spray pyrolysis of a polymeric precursor solution. Chelating agents enable the generation of pure phases under a strictly defined thermal regime. Ce3+ introduction into the host matrix was confirmed by X-ray powder diffraction (XRPD) and luminescence studies.
[Bu4N]2[Ni(btdt)2] (1) ({btdt}2– = 2,1,3-benzenethiadiazole-5,6-dithiolate) was synthesized by treating one equivalent of NiCl2·6H2O with two equivalents of H2btdt in MeOH in the presence of NaOH under nitrogen, and then obtaining a precipitate by adding tetrabutylammonium bromide. When the same reaction is carried out under ambient conditions, it yields the trans-disulfinate complex [Bu4N]2[Ni(btdtO2)2]·H2O (2) along with complex 1. Complex 1 crystallizes in the triclinic space group P$\bar {1}$, whereas complex 2 crystallizes in the monoclinic space group C2/c. The NiII ion, coordinated with four sulfur atoms present in complex 1, shows almost square-planar geometry, but trans-disulfinate complex 2 shows distorted square-planar geometry around the NiII ion with a nonplanar molecular structure. Oxygen atoms of the sulfinates are involved in C–H···O and O–H···O hydrogen-bonding interactions, which might be important factors for the nonplanarity of complex 2. Complex 1 undergoes a reversible oxidation (?E = 0.09 V) at E1/2 = +0.22 V vs. Ag/AgCl and an irreversible oxidation at +0.77 V, whereas complex 2 shows quasi-reversible oxidation at E1/2 = +0.50 V vs. Ag/AgCl in acetonitrile solution.A nickel–dithiolene complex was synthesized. Its oxygenation, which occurs under ambient conditions, results in the isolation of a trans-disulfinate compound. The crystal structures, electronic, and electrochemical properties of the compounds were investigated.
Metastable magnesium hydroxymethoxide [Mg(OH)(OCH3)] powder with nanosheet morphology was derived from a direct bottom-up synthesis using magnesium acetate tetrahydrate as precursor under solvothermal conditions, with benzyl alcohol as structure-directing agent. The synthesis is driven by esterification of magnesium acetate to the corresponding methyl acetate, namely, ligand exchange and esterification of CH3COO– with CH3O–. A MgO powder featuring a Tasker III type (111) surface as its main exposed surface was produced after decomposition of the as-prepared Mg(OH)(OCH3) intermediate. X-ray diffraction (XRD) shows that the as-formed intermediate is Mg(OH)(OCH3), and methyl acetate is identified in the mother liquor by GC–MS measurements. XRD, SEM, and TEM images also show that the surface of the MgO nanosheets is covered by a Tasker III (111) surface. The vanadia supported on this MgO (111) nanosheet surface is more active than the conventional MgO-supported system for the oxidative dehydrogenation of ethylbenzene with carbon dioxide, which is attributed to the oxygen-rich nature and intermediate basicity of the MgO (111) surface.Esterification of magnesium acetate with methanol afforded Mg(OH)(OCH3) nanosheets, whose subsequent thermal decomposition yielded MgO nanosheets covered with Tasker III type (111) surfaces.
Reaction of a copper(I) complex supported by a sterically demanding tripodal tetradentate ligand, HIPT3tren, and O2 gave a mononuclear copper(II) end-on superoxo complex. Spectroscopic (UV/Vis, resonance Raman, ESR, and 1H-NMR) and DFT studies have been performed. The O2-binding process as well as the reaction toward external substrates have been investigated kinetically to demonstrate the unique behavior of the copper(II) end-on superoxo complex, which may occur as a result of the existence of the hydrophobic core around the copper coordination sphere created by the HIPT3tren ligand.Copper(I)-dioxygen reactivity has been examined by using a sterically demanding tripodal tetradentate ligand HIPT3tren. Low-temperature oxygenation of the copper(I) complex afforded a mononuclear copper(II) end-on superoxo complex 1 with a singlet ground state. The O2-binding process as well as the reactivity of 1 toward external substrates has been examined kinetically.
Mono-, bis-, and tris(4-ferrocenyl-1,2,3-triazolylmethyl)arene–?-cyclodextrin adducts have been used to prepare new Pd0 nanoparticle (PdNP) catalysts for C–C cross-coupling reactions in EtOH/H2O. The results show that these catalysts work well in Miyaura–Suzuki and Heck reactions with iodoarenes at 25 and 80 °C, respectively, with turnover numbers (TONs) of up to 31000 for standard Miyaura–Suzuki reactions of PhI when 10 ppm of the Pd catalyst (5 nm PdNPs) were used. The results show the benefit for PdNP catalysis of encapsulating hydrophobic catalytic systems between peripheral water-solubilizing cyclodextrins as bolamphiphile-like materials because the open monoferrocenyltriazolylmethylbenzene system shows a considerably reduced catalytic efficiency compared with bis- and tris(4-ferrocenyl-1,2,3-triazolylmethyl)arene–?-cyclodextrin adducts.Water-soluble “clicked” assemblies containing two or three cyclodextrin-encapsulated ferrocenyl termini and 1,2,3-triazolyl internal ligands for PdII are precursors of stabilized Pd0 nanoparticle precatalysts for efficient Miyaura–Suzuki and Heck reactions of iodobenzene in water/ethanol under mild conditions.
In this paper we describe a rapid and effective wet chemical route to the synthesis of netlike AuCu dimetallic nanowires, in which HAuCl4 and Cu(NO3)2 were co-reduced by NaBH4 in aqueous solution in the presence of surfactant Triton X-100. The nanowires are composed of homogeneous Au–Cu alloy and possess a uniform diameter of around 3.7 nm. The influence of the experimental parameters – including the concentration of the reducing agent and capping agent, kinds of capping agent, and the ratio of Au/Cu – on the formation of AuCu nanowires have been studied. Among the various parameters investigated, copper was found to play a key role in facilitating the formation of nanowires by means of an oriented attachment mechanism. This method can be further extended to the synthesis of other copper-containing dimetallic nanowires such as PtCu and PdCu dimetallic nanowire networks.High-quality and high-yield AuCu dimetallic nanowires were synthesized by a facile method in aqueous solution. Cu plays a key role in inducing the formation of nanowires.
The reactions of the NSO ligands 2-[2-(pyridin-2-yl)ethylthio]acetic acid (HL1), 3-[2-(pyridin-2-yl)ethylthio]propanoic acid (HL2), 2-(carboxymethylthio)-3-(1H-imidazol-4-yl)propanoic acid (H2L3), and 2-(carboxyethylthio)-3-(1H-imidazol-4-yl)propanoic acid (H2L4) with [NEt4]2[ReBr3(CO)3] are presented. Ligands HL1, H2L3, and H2L4 act as tridentate NSO chelators and readily generate the fac-[Re(NSO)(CO)3]complexes Re-L1, Re-HL3, and Re-HL4. Ligand HL2 acts as NSO tridentate chelator only in the presence of base to give complex Re-L2, while without base it coordinates as a NS bidentate chelator to generate complex fac-[ReBr(NS)(CO)3], Re-HL2. All complexes were isolated and characterized by elemental analysis, IR and 1H, 13C NMR spectroscopy. Complex Re-L1, Re-HL2, and Re-HL3 were characterized also by X-ray crystallography. Furthermore, the analogous technetium complexes fac-[99mTc(NSO)(CO)3]+, 99mTc-L1, 99mTc-L2, 99mTc-HL3, and 99mTc-HL4 were synthesized by reacting ligands HL1–H2L4 with the fac-[99mTc(OH2)3(CO)3]+ precursor for 30 min at 75 °C. The tracer complexes 99mTc-L1–99mTc-HL4 were found to be stable in L-cysteine and L-histidine challenge experiments. The bifunctional chelating agents that bear a second carboxylate group are promising for the development of targeted 99mTc radiopharmaceuticals.fac-[Re(NSO)(CO)3] complexes were synthesized with varying chelate ring size and geometry. The order of complex formation preference is: linear (6,5-membered rings) > tripodal (6,5,7-membered rings) > linear (two six-membered rings). The analogous fac-[99mTc(NSO)(CO)3] complexes were prepared in high yield and were stable in solution.
X6Al2HT hydrotalcites, where X represents Fe, Cu, Zn, Ni, Co, Mn or Mg, were synthesized as precursors of catalysts for the toluene and CO total oxidation reactions. Specific area, Fourier transformed infrared spectroscopy analysis, XRD measurements and Thermal analysis of these dried solids were performed. After calcination at 500 °C, different mixed oxides were obtained. The structural analysis (XRD, FTIR) and specific areas of these solids were done. Concerning the total oxidation of toluene, the best activity is obtained with Mn6Al2HT catalyst with T50 at 249 °C. X6Al2 nano-oxides synthesized using hydrotalcite-type solids as precursors, are then very promising candidates for an utilisation as CO and VOC oxidation catalysts. The nature of bivalent cation in these compounds is essential for the efficacy of the catalyst.X6Al2HT hydrotalcites, with X = Fe, Cu, Zn, Ni, Co, Mn or Mg, were synthesized as precursors of catalysts for the toluene and CO total oxidation reactions. The catalytic activity can be established is following order: Mn6Al2HT500 > Co6Al2HT500 = Cu6Al2HT500 > Fe6Al2HT500 > Ni6Al2HT500 >> Zn6Al2HT500 > Mg6Al2HT500.
Two sets of hierarchically structured titania (TiO2) supports were doped with group V metal oxides, one with Nb2O5 and the other with V2O5. It was noted that before thermal treatment the prepared materials were amorphous, whereas after calcination at 400 °C the XRD patterns showed well-defined peaks that indicated that the materials were a crystalline anatase phase. Treating these supports at high temperatures was followed by a decrease in their Brunauer–Emmett–Teller (BET) specific surface area values. The catalytic performance of these materials and their corresponding noble metal (Pd and Au) loaded catalysts was investigated in the total oxidation of toluene. It was clear that after noble-metal loading, the activity was much higher than that of the unloaded supports, with Pd5VTi and PdAu3NbTi offering the best performances in the oxidation reaction. XRD patterns of the noble-metal-loaded catalysts showed peaks associated with the presence of metallic gold particles and palladium species on the supports; diffuse-reflectance UV/Vis spectra also showed the presence of these noble metals, as well as a reduction in the intensities of the bands relative to those in the spectra of the unloaded doped titania supports, which is due to the metal–support interactions. Spectra obtained with this characterization technique also showed a shift of the Au bands to higher wavelengths, which should be correlated to changes in the size of the gold particles.An investigation of the catalytic ability of Nb- and V-doped hierarchically structured TiO2 for the total oxidation of toluene was conducted. An interesting promoting effect was noted for TiO2 doped with Nb and V when compared to a macro-mesoporous titania support. This effect was also studied after the doped TiO2 materials were loaded with noble metals. The noble-metal-loaded materials displayed better catalytic performance at low conversion temperatures than the unloaded supports.
Using [Ln(L)8]3+ [Ln = Tb, Y; L = dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF)] cations as templating reagents, the syntheses and crystal structures of the following new metal organic–inorganic hybrid complexes based on either discrete clusters or 1D chains of an iodoplumbate or-bismuthate moiety are reported: [Tb(DMSO)8]2[(DMSO)2Pb5I16] (1), [Tb(DMF)8][Pb3I9]1?·DMF (2) and [Ln(DMF)8][Bi2I9] [Ln = Y (3), Tb (4)]. These derivatives were characterized by thermogravimetric analysis (TGA), diffuse-reflectance spectroscopy, luminescence spectroscopy and magnetic studies. TGA studies show that the thermal stability of these complexes decreases in the order 2 > 3 ? 4 > 1. An optical band-gap in the range 1.90–2.15 eV in the diffuse-reflectance spectra of 1–4 indicate their potential use as semiconductors, 3 and 4 being the most promising because of their low band gap values. Compared to the precursors [Tb(DMSO)8]I3 and [Tb(DMF)8]I3, the high energy transitions in the excitation spectra of 1, 2 and 4 are quenched by a process that is best attributed to the autoionization of the carriers in the material. The temperature dependence of the magnetic susceptibilities of 1, 2 and 4 was reproduced well by a Curie–Weiss plot at 2–300 K.New hybrid complexes composed of metal–organic cations with a magnetic/luminescent terbium centre and iodometallate anions derived from the neutral semiconductor PbI2 and BiI3 are reported, and the solvent-induced interconversion among the iodoplumbate derivatives is described.
Microwave-assisted synthesis represents a valuable improvement in the domains of molecular and organic chemistry and was recently extended to inorganic and materials chemistry. A comparison of titanium dioxide nanoparticles synthesised in aqueous solution prepared in a microwave or a conventional oven is presented here. More precisely, three different protocols were used in order to determine the impact of the heating mode on the final product in terms of crystalline structure, particle size and morphology. Therefore, the resultant powders were analysed by Raman spectroscopy as well as X-ray and electron diffraction and transmission electron microscopy. The results show that microwave treatment significantly reduces the heating time and generally produces smaller nanoparticles. The rutile/anatase/brookite phase distribution is also modified by the heating mode in certain protocols up to the formation of a pure anatase phase, for instance. The impact of microwaves on the solvent and on the inorganic precursors has been demonstrated. A photocatalytic test and time-resolved microwave conductivity experiments were performed on rather similar samples prepared with the two heating modes in order to probe the improvement of the crystalline quality and its consequences on the photocatalytic activity of the TiO2 material.In the present study of TiO2 nanomaterials elaborated in aqueous conditions, it is demonstrated that microwave-assisted synthesis may significantly change the structure and size of nanoparticles in comparison with conventional heating although it does not systematically improve the targeted property.
This paper shows how supporting the Dawson heteropoly compound (HPC) (NH4)6P2Mo18O62 opens up the possibility to enhance its catalytic activity by controlling its molecular behaviour. The effect of parameters such as the loading of the Dawson species onto a support and the nature of its interaction is explored by IR and Raman spectroscopy and correlated with its performance in the oxidation of propene. Active species in propene oxidation were formed during the Dawson HPC rearrangement occurring on a TiO2 support. When supported, the Dawson (NH4)6P2Mo18O62 HPC is beneficially activated during the catalytic process, which led to the formation of a supported active species. A conversion stability observed for the HPC/TiO2 samples with loading above 5 wt.-% revealed that the Dawson HPC had to interact with the support to develop a stable activity. This arrangement seemed indeed to be the most suitable to reach a high conversion. On the contrary, it was proposed that isolated HPC species were more prone to destabilization due to the loss of the proximity between the anions in the HPC crystal lattice. This work will show that the catalytic systems operated very efficiently due to the redox properties of molybdenum atoms when in an HPC 3D framework. This could not have happened with low loadings as only fragments of the HPCs were present on the surface. The stabilization of catalytic activities observed in the supported catalysts with high loadings was associated with the stabilization of a Keggin-like supported phase.This paper shows how supporting the Dawson (NH4)6P2Mo18O62 heteropoly compound opens up the possibility to enhance its activity in propene oxidation by controlling its molecular behaviour. The effect of parameters such as the loading of the Dawson species onto a support and the nature of its interaction is correlated with its performance.
The synthesis of metal oxide nanosheets using a lamellar phase as a template effectively modified the nanosheets because surfactant molecules surround the entire surface of the nanosheets. Here, we show the development of layered titanate nanosheets with a lamellar mesostructure. The layered titanate nanosheet forms by using the lamellar self-assembly of cationic dodecanediamine as a template and an electrostatic interaction between negatively charged titanate nanosheets and positively charged 1,12-dodecanediamine during hydrothermal synthesis. This approach leads to titanate nanosheets with new properties such as visible light absorption and a high adsorption of cationic organic compounds, which results in the effective photodegradation of Rhodamine B under visible-light irradiation. This approach has important implications for the use of metal oxide nanosheets in environmental and industrial applications.Layered titanate nanosheets with a lamellar mesostructure were synthesized using lamellar self-assembly as a template. Effective surface modification of the nanosheets led to visible light absorption and high adsorption of cationic organic compounds, which led to the effective photodegradation of Rhodamine B under visible-light irradiation.
A series of one-dimensional heterotrimetallic assemblies, [Cu2Ln(L)2(H2O)4][M(CN)6]·nH2O [Ln = Gd, M = Co (1), Fe (2), Cr (3), and Ln = La, M = Co (4), Fe (5), Cr (6)], were prepared by the reaction of a Cu2Ln precursor complex, [Cu2Ln(L)2(NO3)3], with K3[M(CN)6] in water. All of the assemblies were isomorphous and formed a 1D zigzag chain, in which the [Cu2Ln(L)2(H2O)4]3+ and [M(CN)6]3– units were alternately positioned and were linked in a Cu–NC–M–CN–Cu manner. Compound 1 showed magnetic behaviour similar to that of the discrete precursor complex, [Cu2Gd(L)2(NO3)3], owing to the diamagnetic nature of the [CoIII(CN)6]3– unit. In the case of 2, a simple summation of the magnetic behaviour of the [Cu2Gd(L)2(H2O)4]3+ and [Fe(CN)6]3– units was observed, whereas ferromagnetic interactions were found to be operative between the Cu2+ and Cr3+ ions in compound 3. The same magnetic interactions between Cu2+ and M3+ were confirmed in compounds 4 to 6, which included the diamagnetic La3+ ion. The differences in the magnetic behaviours of 2 and 3 can be explained by the overlap of the d?z?2(Cu)–p?(CN) orbitals in the bent Cu–N?C linkage and the spin-density on the cyanide nitrogen of the [Cr(CN)6]3– unit.Novel cyanide-bridged assemblies that have ordered alternate arrays of three types of paramagnetic metal centres were obtained from the reaction of preorganized heterobimetallic trinuclear complexes, [Cu2Ln(L)2(NO3)3] (LnIII = Gd, La) and K3[M(CN)6] (MIII = Co, Fe, Cr). These form a 1D zigzag chain that is extended by the MIII–CN–CuII linkages and exhibit different magnetic behaviour, which depends on the combination of the metal ions.
Highly multibranched gold nanostars were obtained by a room-temperature synthesis assisted by deep-eutectic solvents (DES). The concentration of the ascorbate ions and the presence of water in the solution were found to both have a profound influence on branch formation. A growth mechanism of the nanostar is therefore proposed from the analysis of the particle dimensions, the aspect ratio of their protuberances, and the gold crystal size. These spiky nanoparticles would find an application as conductive filler in polymeric piezoresistive composites, based on a tunneling conduction mechanism.The dimension and morphology of gold nanostars, prepared through a room-temperature synthesis assisted by deep-eutectic solvents, can be tuned by varying the concentration of water and L-ascorbic acid. The obtained shapes fit with the requirements for the preparation of piezoresistive composites based on a tunneling conduction mechanism.
Hydroxyapatite (HAP) microspheres composed of nanorods have successfully been prepared by a facile co-precipitation method without any template. We propose the formation mechanism of the microspheres to be a four-step process on the basis of the evolution of their morphology as a function of reaction time. We investigate the competitive sorption of the HAP microspheres for Pb2+, Cu2+, Cd2+, Zn2+, and Ni2+ to show that HAP microspheres are a highly selective adsorbent for Pb2+ in wastewater.Hierarchically structured microspheres self-assembled from hydroxyapatite nanorods have successfully been prepared by a simple co-precipitation method without any template. The as-prepared materials exhibit high selective adsorption for Pb2+ in wastewater.
Conflicting results have been reported with respect to the photoinduced switching of the magnetic properties of [FeIII(salten)]+ complexes [salten = 4-azaheptamethylene-1,7-bis(salicylideneiminate)] coordinated by photoisomerizable ligands. In order to address this problem, two FeIII complexes [Fe(salten)(3-azpy)]BPh4 (1) and [Fe(salten)(4-azpy)]BPh4 (2) have been synthesized and characterized by various physicochemical methods (azpy = phenylazopyridine). Both 1 and 2 exhibit a low spin (S = 1/2) to high spin (HS, S = 5/2) transition in the solid state. In solution at room temperature both complexes are predominantly HS. Upon exposure to 310 (trans ? cis) and 440 nm radiation (cis ? trans) the free and coordinated 3- and 4-azpy ligands undergo a reversible cis–trans isomerization. For 2 a corresponding reduction of the HS fraction 2?% is observed, whereas in 1 no effect is observed. Extensive DFT calculations, which employ different functionals and basis sets, explain this experimental result. The consequences of these findings with respect to the design of spin-switchable iron(III) complexes with photoactive ligands are discussed.[Fe(salten)(3-azpy)]BPh4 (1) and [Fe(salten)(4-azpy)]BPh4 (2) have been synthesized and characterized [salten = 4-azaheptamethylene-1,7-bis(salicylideneiminate), azpy = phenylazopyridine]. Both exhibit a low to high spin transition in the solid state and are predominantly high spin in solution. cis–trans isomerization of coordinated azpy leaves their spin equilibria almost unaffected.
?- and ?-Fe2O3 nanorods have been prepared from a ?-FeOOH precursor that was obtained by aqueous-phase precipitation of ferric chloride. The oxyhydroxide precursor had a rodlike shape with a diameter of 30–40 nm and a length of 400–500 nm. Calcination at 500 °C of the rod-shaped oxyhydroxide in air yielded ?-Fe2O3 nanorods, whereas heating to reflux in polyethylene glycol (PEG) at 200 °C resulted in the formation of ?-Fe2O3 nanorods. Both oxides inherited the rodlike morphology of the precursor but exposed different crystalline facets. When being used to catalyze NO reduction by CO, an environmentally important reaction in NO abatement, the ?-Fe2O3 nanorods were much more active than the ?-Fe2O3 nanorods and showed an apparent crystal-phase effect. This was because the ?-Fe2O3 nanorods simultaneously exposed iron and oxygen ions on their surfaces, which facilitated the adsorption and activation of NO and CO molecules.?- and ?-Fe2O3 nanorods were obtained by proper dehydration of a rod-shaped ?-FeOOH precursor. The Fe2O3 nanorods showed a distinct crystal-phase effect in the reduction of NO by CO on the basis of their exposed surface facets.
Heterobimetallic lithium–iron coordination compounds are interesting targets for several reasons: they can be used as precursors for mixed metal oxides, as catalysts, for example, for ring-opening polymerization reactions or to study oxidation/reduction processes. Finally their magnetic properties are also of interest. New heterobimetallic aryloxide complexes, namely [(thf)4Li3Fe(OPh)3(O2C6H4)Cl]2 (1), [{(thf)3Li3Fe(OPh)5Cl}3]n (2), and [(thf)3Li3Fe(OPh)6]2 (3), have been synthesized and characterized by single-crystal X-ray diffraction. While compounds 1 and 3 were synthesized by an oxidative substitution reaction, compound 2 was directly obtained from the FeIII salt. These compounds are accessible by both synthetic pathways. Additionally, in compound 1, the phenoxy ligand was catalytically oxidized to ortho-catechol, which was incorporated into the structure of 1 as a ligand that coordinates strongly to iron. All compounds feature the FeIII ion with a trigonal, bipyramidal environment, with coordination number 5.Three new pentacoordinate FeIII complexes, [(thf)4Li3Fe(OPh)3(O2C6H4)Cl]2 (1), [{(thf)3Li3Fe(OPh)5Cl}3]n (2), and [(thf)3Li3Fe(OPh)6]2 (3), two dinuclear, molecular species (1 and 3) and one trinuclear 1D coordination polymer, are reported. Compound 1 has a coordination sphere close to a square pyramid and might thus be useful for applications such as catalyst for the ring-opening polymerization of lactide.
Bimodal magnetic resonance imaging (MRI)/optical probes for bioimaging were obtained by grafting two types of lanthanide metal ions, Gd3+ and Eu3+/Tb3+, on the surface of SiO2 nanoparticles. The resulting systems were endowed with relaxometry and photoluminescent properties, respectively. Grafting a pyridine-based aromatic backbone on to the silica surface enhances the emission quantum yield of the Eu3+-containing nanoparticles fivefold compared to similar systems that bear no aromatic antennae. The emission properties of the mixed Ln3+/Gd3+-based nanoparticles are not influenced by the presence of Gd3+. The relaxometric properties of these samples are slightly better than the properties of commercial [Gd(DTPA)]2 (DTPA = diethylenetriaminepentaacetate). When taken up by RAW 264.7 cells (mouse macrophage cell line), such bimodal probes exhibit both T1-weighted MRI increased contrast and fluorescence tracking.Grafting two lanthanides, Gd3+and Eu3+/Tb3+, to a single SiO2 nanoparticle provides a bimodal bioimaging probe with luminescent and magnetic functionalities. The use of a pyridine bridge enhances the Ln3+ emission properties. After internalization in mouse macrophage cells, the bimodal probes exhibit both T1-weighted MRI increased contrast and efficient optical tracking by fluorescence.
New hybrid compounds have been synthesized by functionalization of cobalt and copper layered hydroxides by salen complexes. Two kinds of compounds have been obtained from [M(SalenSO3Na2)] (M = Cu2+, Ni2+, Co2+ and Zn2+) and the preintercalated copper and cobalt hydroxides Cu2(OH)3(DS) and Co2(OH)3(DS0) [SalenSO3Na2 = N,N?-bis(5-sulfonatosalicylidene)-1,2-diaminoethane disodium salt, DS– = dodecylsulfate, DS0– = dodecylsulfonate]. The reaction of [M(SalenSO3Na2)] with layered copper hydroxide led to the anion-exchanged compounds Cu2(OH)3.00(CuSalenSO3)0.50·0.20H2O [Cu(SalenSO3)?Cu (1)] and Cu2(OH)3.24(NiSalenSO3)0.38·2.6H2O [Ni(SalenSO3)?Cu (2)] where M = Cu2+ or Ni2+. Similarly, the reaction with layered cobalt hydroxide leads to the exchanged compounds Co2(OH)3.18(NiSalenSO3)0.41·4.0H2O [Ni(SalenSO3)?Co (6)] and Co2(OH)3.44(CoSalenSO3)0.28·3.7H2O [Co(SalenSO3)?Co (8)] where M = Ni2+ or Co2+. The reaction of [M(SalenSO3)Na2] with layered copper hydroxide where M = Co2+ or Zn2+ and that of layered cobalt hydroxide where M = Cu2+ or Zn2+ resulted in the modification of the host structure because of concomitant partial cation exchange between the salen complex and the inorganic layers. Mixed-ion-exchanged compounds were obtained, Cu1.16Co0.84(OH)3.28(CoSalenSO3)0.36·6.4H2O [Co(SalenSO3)?Cu/Co (4)], Cu0.7Zn1.30(OH)3.20(ZnSalenSO3)0.40·2.11H2O [Zn(SalenSO3)?Cu/Zn (3)], Co1.72Cu0.28(OH)3.28(CuSalenSO3)0.36·3.20H2O [Cu(SalenSO3)?Co/Cu (5)] and Co0.80Zn1.20(OH)3.20(ZnSalenSO)0.40·2.25H2O [Zn(SalenSO3)?Co/Zn (7)]. The magnetic behaviour of the compounds is drastically modified depending on the structure of the inorganic layers induced by the functionalization and partial cation exchange. The hybrid copper layered hydroxides show antiferromagnetic (for 3) or weak ferromagnetic (for 1, 2 and 4) behaviour. The cobalt analogues 5, 6 and 8 are ferrimagnets with ordering temperatures at ca. 6 K, whereas the Co/Zn heterometallic layered simple hydroxide 7 presents dominant antiferromagnetic interactions.Insertion–grafting of salen-type complexes into copper and cobalt layered hydroxides leads to a drastic modification of the structure and composition of the inorganic layers. The magnetic properties of the heterometallic hybrid layered hydroxides obtained depend strongly on the modification of the inorganic layers induced by the insertion–grafting reaction.
The use of ?-benzoin oxime (bzoxH2) in copper(II) benzoate chemistry, in the absence or presence of ancillary azido ligands, is reported. The reaction of Cu(O2CPh)2·2H2O with one equivalent of bzoxH2 in N,N-dimethylformamide (DMF) affords the decanuclear complex [Cu10(bzox)10(DMF)4] (1) in good yield. Dissolution of 1 in CH2Cl2 leads to the subsequent isolation of the solvent-free complex [Cu10(bzox)10] (2) in moderate yields. Complexes 1 and 2 are isostructural and possess a loop or single-strand molecular wheel topology. The bzox2– dianions behave as ?1:?1:?2:?3 ligands, which give rise to an overall [Cu10(?-ONR)10(?-OR?)10] core. Both 1 and 2 stack to form nanotubular columns with beautiful supramolecular architectures. The reaction of Cu(O2CPh)2·2H2O with bzoxH2 and NaN3 in a 1:1:1 molar ratio in MeOH gives the bzoxH2-free complex [Cu(N3)(O2CPh)(MeOH)]n (3), which is a 1D chain. The CuII atoms in 3 are linked by a single, end-on N3– group, a syn,syn-?1:?1:? PhCO2– ion, and an oxygen atom from the bridging MeOH ligand. The 1D chains are hydrogen bonded into 2D sheets through Nazide···H(OMeOH) interactions. Variable-temperature, solid-state direct-current magnetic studies were carried out on 1–3. The data for 1 and 2 indicate very strong antiferromagnetic exchange interactions and a S = 0 ground state, which is expected for even-membered loop arrays of CuII atoms. In contrast, 3 exhibits ferromagnetic exchange interactions; the data were fitted to the appropriate equation derived from the Hamiltonian H = –J?(Si·Si+1), which includes a zJ? interchain interaction term. The best-fit parameters were J = +49.6(4) cm–1, g = 2.067(3), and zJ? = 2.3(1) K. The combined results demonstrate the ligating flexibility of both the bzoxH2 and azido groups and their usefulness in the synthesis of polynuclear CuII clusters and coordination polymers.The reaction illustrated gives the decanuclear complexes [Cu10(bzox)10(DMF)4] and [Cu10(bzox)10] (bzoxH2 = ?-benzoin oxime, DMF = N,N-dimethylformamide), which have a single-strand wheel topology, andthe 1D chain [Cu(N3)(O2CPh)(MeOH)]n. The Cu10 clusters are both antiferromagnetically coupled with S = 0 ground states, whereas the 1D chain consists of ferromagnetically coupled S = 1/2 CuII ions.
A new family of terpyridine (terpy)-based spin-crossover cobalt(II) complexes, [Co(HO–Cn-terpy)2](BF4)2 [n = 6 (1), 8 (2), 10 (3), 12 (4), and 14 (5)] that possesses a hydroxy-appended long alkyl chain present on the terpyridine skeleton was synthesized and characterized by X-ray structure analysis and temperature-dependent magnetic susceptibility. In the solid state, the compounds 1·H2O, 4, and 5·H2O were crystallized in the triclinic P$\bar {1}$ space groups, and their central cobalt(II) ion was coordinated by six nitrogen atoms from two terpyridine units to form a pseudo-octahedral symmetry. In the case of 1·H2O, one of the terminal hydroxy substituents was involved in hydrogen bonding with a water molecule. For compound 4, on the other hand, both of terminal hydroxy units form a short intermolecular contact with the BF4– anion. The temperature-dependent magnetic behavior of 1 and 2 showed a gradual spin crossover, whereas 3 and 4 revealed an abrupt spin transition with a wide thermal hysteresis loop (?T = 21 K, T1/2? = 316 K, and T1/2? = 295 K for 3; ?T = 40 K, T1/2? = 348 K, and T1/2? = 308 K for 4), and 5 exhibits “reverse spin transition” (?T = 17 K, T1/2? = 214 K, andT1/2? = 231 K). It has been suggested that compounds 3 and 4 form stronger intermolecular interactions through the fastener effect and hydrogen bonding than 1 and 2. On the basis of a comparison of the resulting magnetic behaviors of the compounds that contain long alkyl chains with a hydroxy group at the end, it was found that the long alkyl chains with the terminal hydroxy group could induce stronger intermolecular interactions between molecules. However, there are many short contacts through the counteranions for 5·H2O, but thermal motion of the long alkyl chains can be expected. Compound 5 exhibits “reverse spin transition” induced by a structural phase transition.Cobalt(II) complexes with hydroxy-appended long alkyl chains at the end were synthesized. They were studied by single-crystal X-ray analysis and SQUIDmeasurement. For differences in magnetic behavior, we considered two factors: (i) a fastener effect and (ii) hydrogen bonding by the OH group.
Microwave chemistry is becoming a very attractive synthesis technique in many areas of synthetic chemistry. In particular, the utilization of this method to fabricate nanostructured materials is a fast growing research area with immense potential. Similarly, the use of sacrificial scaffolds has been demonstrated as an effective route to achieve intricate 2D and 3D porous architectures. Here, we present an extremely fast and versatile synthetic approach based on microwave heating to fabricate complex macroporous magnetic frames using sacrificial templates. In just a few minutes, a stoichiometric and homogeneous conformal nanometric coating of superparamagnetic nanoparticles was grown onto a 2D monolayer formed by self-assembled polystyrene colloids. No post-treatment was required, the sacrificial polystyrene template was removed simultaneously as the magnetic nanoparticles formed, and large-scale structural order was preserved.The fabrication of porous magnetic nanoarchitectures by microwave heating is reported. In addition to drastically decreasing the time for the synthesis, other characteristics of the technique, i.e. reaction kinetics, diffusivity and selectivity, have been exploited.
We report a cyano-bridged V–Nb bimetal assembly, K0.59VII1.59VIII0.41[NbIV(CN)8]·(SO4)0.50·6.9H2O, exhibiting ferrimagnetism with a high Curie temperature (TC) of 210 K, which is the highest TC value among those of octacyano-bridged bimetal assemblies. Such a high TC value originates from the high coordination number of octacyanoniobate and the strong superexchange interaction between VII (S = 3/2) and NbIV (S = 1/2) through the CN groups.We prepared a V–Nb octacyano-bridged bimetal assembly, K0.59VII1.59VIII0.41[NbIV(CN)8]·(SO4)0.50·6.9H2O, with a high Curie temperature (TC) of 210 K, which is the highest TC among those of other octacyanometalate-based compounds. The high coordination number of octacyanoniobate and the strong superexchange interaction between VII (S = 3/2) and NbIV (S = 1/2) through the CN groups are the reasons for such a high value.
A vanadium 2,6-naphthalenedicarboxylate, VIII(OH)(O2C–C10H6–CO2)·H2O, denoted as COMOC-3as (COMOC = Center for Ordered Materials, Organometallics and Catalysis, Ghent University), has been synthesized under hydrothermal conditions by means of both a solvothermal and a microwave synthesis procedure. The structure shows the topology of an aluminium 2,6-naphthalenedicarboxylate, the so-called MIL-69 (MIL = Materials of the Institute Lavoisier). After calcination at 250 °C in air, the VIII center was oxidized to VIV with the structure of VIVO(O2C–C10H6–CO2) (COMOC-3). The oxidation process was verified by cyclic voltammetry and EPR spectroscopy. The crystallinity was investigated by variable-temperature XRD. The title compound is stable against air and moisture. The catalytic performance of COMOC-3 was examined in the liquid-phase oxidation of cyclohexene. COMOC-3 exhibited similar catalytic performance to MIL-47 [VO(O2C–C6H4–CO2)]. The compound is reusable and maintains its catalytic activity through several runs.A vanadium-based metal–organic framework (COMOC-3) has been synthesized and fully characterized. It crystallizes in the monoclinic system with the space group C2/c (no. 15). This closed MIL-69 analogue shows excellent thermal stability and good catalytic performance in the liquid-phase oxidation of cyclohexene. The catalyst can be regenerated and reused without significant loss of activity.
Thermally driven heat pumps can significantly help to minimize primary energy consumption and greenhouse gas emissions generated by industrial or domestic heating and cooling processes. This is achieved by using solar or waste heat as the operating energy rather than electricity or fossil fuels. One of the most promising technologies in this context is based on the evaporation and consecutive adsorption of coolant liquids, preferably water, under specific conditions. The efficiency of this process is first and foremost governed by the microporosity, hydrophilicity, and hydrothermal stability of the sorption material employed. Traditionally, inorganic porous substances like silica gel, aluminophosphates, or zeolites have been investigated for this purpose. However, metal–organic frameworks (MOFs) are emerging as the newest and by far the most capable class of microporous materials in terms of internal surface area and micropore volume as well as structural and chemical variability. With further exploration of hydrothermally stable MOFs, a large step forward in the field of sorption heat pumps is anticipated. In this work, an overview of the current investigations, developments, and possibilities of MOFs for use in heat pumps is given.This review introduces metal–organic frameworks (MOFs) as a promising new class of microporous materials for use in adsorption heat transformation applications. The water adsorption characteristics of several MOFs are summarized, including heat of adsorption and cycle stability, which show the tremendous potential of MOFs in thermally driven heat pumps.
The synthesis and characterisation of four new Schiff base-like ligands with long alkyl chains in the outer periphery and their iron(II) complexes with methanol and pyridine as axial ligands is reported. Two of the methanol complexes crystallise in a lipid layer-like arrangement with the alkyl chain (tail) packed in the middle and the iron centres (head) in the outer sites. The pyridine complexes show varying types of spin transition (step wise, incomplete, with hysteresis), which depends on the alkyl chain length and substituents in the outer periphery of the ligand. Investigations in solution using 1H NMR spectroscopy demonstrate that the differences in the spin transition behaviour are due to packing effects as the same transition curve is obtained independently of the alkyl chain length.A series of iron(II) complexes with head–tail character have been investigated. Lipid layer-like structures have been observed,and the complexes with pyridine show spin crossover behaviour.
Mesoporous zirconium phosphonate materials with bridged organic groups in the framework were hydrothermally synthesized with 1-hydroxyethylidene-1,1-diphosphonic acid as coupling molecule and cetyltrimethylammonium bromide as template. The mesostructure is wormhole-like with a specific surface area of 702 m2/g and a uniform pore size of 3.6 nm, and the organophosphonate groups are homogeneously integrated in the network of the obtained solids. The hydroxyethylidene-bridged mesoporous zirconium phosphonates can serve as solid-acid catalysts for the synthesis of methyl-2,3-O-isopropylidene-?-D-ribofuranoside from D-ribose and exhibit high catalytic activity with rapid reaction rate, which are comparable to the catalytic performance when liquid acid HCl or commercial ion-exchange resin NKC-9 is used as catalyst. Furthermore, mesoporous zirconium phosphonates show high stability with good reusability without any loss of catalytic activity after five cycles, which demonstrates their potential for industrial applications.Wormhole-like mesoporous hydroxyethylidene-bridged zirconium organophosphonates with a surface area of 702 m2/g and a pore size of 3.6 nm were synthesized and used as effective solid-acid catalysts in the condensation reaction of D-ribose with acetone and methanol to produce methyl-2,3-O-isopropylidene-?-D-ribofuranoside.The catalyst shows good reusability with high activity.
Posted on 6 December 2011 | 11:10 am
Other notes:
Information about this site:
The author- or copyrights of
the listed Internet pages are held by
the respective authors or site
operators, who are also responsible for
the content of the presentations.
To see your page listed here: Send us an
eMail! Condition: Subject-related
content on chemistry, biochemistry and
comparable academic disciplines!
Citation:
http://www.internetchemistry.com/rss/eurjic.php
Keywords:
Chronological list of recent
articles on Chemistry, Inorganic Chemistry,
European Journal of Inorganic Chemistry.
