Showing papers in "Inorganic Chemistry in 2009"
TL;DR: This paper reviews recent achievements in heterometal complexes, oligonuclear complexes for studying the nature of the 3d-4f exchange interaction; construction of single-molecule magnets; and magnetic properties of 3d/4f coordination polymers.
Abstract: Heterometallic 3d−4f complexes are of high interest in molecular magnetism: the lanthanide ions bring large and, in most cases, anisotropic magnetic moments. The combination of 3d and 4f metal ions, which differ through their chemistries and stereochemical preferences, leads to a rich variety of heterometal complexes, ranging from discrete entities to 3-D coordination polymers. This paper reviews recent achievements in this field: (i) oligonuclear complexes for studying the nature of the 3d−4f exchange interaction; (ii) construction of single-molecule magnets; (iii) magnetic properties of 3d−4f coordination polymers.
479 citations
TL;DR: The first two families of polyoxometalate-based single-molecule magnets (SMMs) are reported here and the ligand-field parameters and the splitting of the J ground-state multiplet of the lanthanide ions have been also estimated.
Abstract: The first two families of polyoxometalate-based single-molecule magnets (SMMs) are reported here. Compounds of the general formula [Ln(W5O18)2]9− (LnIII = Tb, Dy, Ho, and Er) and [Ln(SiW11O39)2]13− (LnIII = Tb, Dy, Ho, Er, Tm, and Yb) have been magnetically characterized with static and dynamic measurements. Slow relaxation of the magnetization, typically associated with SMM-like behavior, was observed for [Ln(W5O18)2]9− (LnIII = Ho and Er) and [Ln(SiW11O39)2]13− (LnIII = Dy, Ho, Er, and Yb). Among them, only the [Er(W5O18)2]9− derivative exhibited such a behavior above 2 K with an energy barrier for the reversal of the magnetization of 55 K. For a deep understanding of the appearance of slow relaxation of the magnetization in these types of mononuclear complexes, the ligand-field parameters and the splitting of the J ground-state multiplet of the lanthanide ions have been also estimated.
447 citations
TL;DR: A network-structured SnO(2)/ZnO heterojunction nanocatalyst with high photocatalytic activity was successfully synthesized through a simple two-step solvothermal method and is characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscope, N(2) physical adsorption, and UV-vis spectroscopy.
Abstract: A network-structured SnO2/ZnO heterojunction nanocatalyst with high photocatalytic activity was successfully synthesized through a simple two-step solvothermal method. The as-synthesized samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, N-2 physical adsorption, and UV-vis spectroscopy. The results show that the SnO2/ZnO sample with a molar ratio of Sn/Zn = 1 is a mesoporous composite material composed of SnO2 and ZnO. The photocatalytic activity of SnO2/ZnO heterojunction nanocatalysts for the degradation of methyl orange is much higher than those of solvothermally synthesized SnO2 and ZnO samples, which can be attributed to the SnO2-ZnO heterojunction, the pore structure, and higher Brunauer-Emmeff-Teller (BET) surface area of the sample: (1) The SnO2-ZnO heterojunction improves the separation of photogenerated electron-hole pairs due to the potential energy differences between SnO2 and ZnO, thus enhancing the photocatalytic activity. (2) The SnO2/ZnO sample might possess more surface reaction sites and adsorb and transport more dye molecules due to the higher BET surface area and many pore channels, also leading to higher photocatalytic activity.
358 citations
TL;DR: Simple theoretical approaches used for understanding typical SCM behavior and some rational synthetic strategies to obtain SCM materials are summarized together with representative examples of SCMs previously reported.
Abstract: Slow relaxation of the magnetization (i.e., "magnet-like" behavior) in materials composed of magnetically isolated chains was observed for the first time in 2001. This type of behavior was predicted in the 1960s by Glauber in a chain of ferromagnetically coupled Ising spins (the so-called Glauber dynamics). In 2002, this new class of nanomagnets was named single-chain magnets (SCMs) by analogy to single-molecule magnets that are isolated molecules displaying related superparamagnetic properties. A long-range order occurs only at T = 0 K in any pure one-dimensional (1D) system, and thus such systems remain in their paramagnetic state at any finite temperature. Nevertheless, the combined action of large uniaxial anisotropy and intrachain magnetic interactions between high-spin magnetic units of the 1D arrangement promotes long relaxation times for the magnetization reversal with decreasing temperature, and finally at significantly low temperatures, the material can behave as a magnet. In this Forum Article, we summarize simple theoretical approaches used for understanding typical SCM behavior and some rational synthetic strategies to obtain SCM materials together with representative examples of SCMs previously reported.
353 citations
TL;DR: The chemistry of these three italicized areas is developed, and from this platform, discovery paths leading to new hydrohalic acid- and water-splitting catalysts are delineated and a highly manufacturable and inexpensive method for solar PE storage has been discovered.
Abstract: Personalized energy (PE) is a transformative idea that provides a new modality for the planet’s energy future. By providing solar energy to the individual, an energy supply becomes secure and available to people of both legacy and nonlegacy worlds and minimally contributes to an increase in the anthropogenic level of carbon dioxide. Because PE will be possible only if solar energy is available 24 h a day, 7 days a week, the key enabler for solar PE is an inexpensive storage mechanism. HY (Y = halide or OH−) splitting is a fuel-forming reaction of sufficient energy density for large-scale solar storage, but the reaction relies on chemical transformations that are not understood at the most basic science level. Critical among these are multielectron transfers that are proton-coupled and involve the activation of bonds in energy-poor substrates. The chemistry of these three italicized areas is developed, and from this platform, discovery paths leading to new hydrohalic acid- and water-splitting catalysts are...
351 citations
TL;DR: Solid-state NMR spectra unequivocally demonstrate the presence of the guest species, as well as the successful postsynthetic functionalization of the MIL-53, which leads to a porous compound that exhibits hysteresis behavior in the N(2) sorption experiments.
Abstract: Aluminum aminoterephthalate Al(OH)[H2N−BDC]·0.3(H2N−H2BDC (denoted MIL-53−NH2(as)) was synthesized under hydrothermal conditions. The activation of the compound can be achieved in two steps. The treatment with DMF at 150 °C leads to Al(OH)[H2N−BDC]·0.95DMF (MIL-53−NH2(DMF)). In the second step, DMF is thermally removed at 130 °C. Upon cooling in air, the hydrated form Al(OH)[H2N−BDC]·0.9H2O (MIL-53−NH2(lt)) is obtained. The dehydration leads to a porous compound that exhibits hysteresis behavior in the N2 sorption experiments. The MIL-53−NH2(lt) can be modified by postsynthetic functionalization using formic acid, and the corresponding amide Al(OH)[HC(O)N(H)−BDC]·H2O (MIL-53−NHCHO) is formed. All four phases were thoroughly characterized by X-ray powder diffraction, solid-state NMR and IR spectroscopy, and sorption measurements, as well as thermogravimetric and elemental analysis. Based on the refined lattice parameter similar breathing behavior of the framework as found in the unfunctionalized MIL-53 can...
350 citations
TL;DR: The most effective electron acceptor for hydrogen evolution is found to be complex 2, which provides the fastest luminescence quenching rate constant for C1, which depends on many factors, including the stability of the catalysts, the driving force for proton reduction, and the relative and absolute concentrations of system components.
Abstract: A series of cobaloxime complexes—([Co(dmgH)2pyCl] (1), [Co(dmgH)2(4-COOMe-py)Cl] (2), [Co(dmgH)2(4-Me2N-py)Cl] (3), [Co(dmgH)(dmgH2)Cl2] (4), [Co(dmgH)2(py)2](PF6) (5), [Co(dmgH)2(P(n-Bu)3)Cl] (6), and [Co(dmgBF2)2(OH2)2] (7), where dmgH = dimethylglyoximate monoanion, dmgH2 = dimethylglyoxime, dmgBF2 = (difluoroboryl)dimethylglyoximate anion, and py = pyridine—were synthesized and studied as molecular catalysts for the photogeneration of hydrogen from systems containing a Pt terpyridyl acetylide chromophore and triethanolamine (TEOA) as a sacrificial donor in aqueous acetonitrile. All cobaloxime complexes 1−7 are able to quench the luminescence of the Pt(II) chromophore [Pt(ttpy)(C≡CPh)]ClO4 (C1) (ttpy = 4′-p-tolyterpyridine). The most effective electron acceptor for hydrogen evolution is found to be complex 2, which provides the fastest luminescence quenching rate constant for C1 of 1.7 × 109 M−1 s−1. The rate of hydrogen evolution depends on many factors, including the stability of the catalysts, the d...
327 citations
TL;DR: H(2)O is a highly efficient photocatalyst under visible light and samples recovered from repeated photooxidation experiments are almost identical to the as-prepared samples, proving the stability of Ag/AgBr/WO(3).
Abstract: A new composite photocatalyst Ag/AgBr/WO3·H2O was synthesized by reacting Ag8W4O16 with HBr and then reducing some Ag+ ions in the surface region of AgBr particles to Ag nanoparticles via the light-induced chemical reduction. Ag nanoparticles are formed from AgBr by the light-induced chemical reduction reaction. The Ag/AgBr particles are on the surface of WO3·H2O and have irregular shapes with sizes varying between 63 and 442 nm. WO3·H2O appears as flakes about 31 nm thick and 157−474 nm wide. The as-grown Ag/AgBr/WO3·H2O sample shows strong absorption in the visible region because of the plasmon resonance of Ag nanoparticles in Ag/AgBr/WO3·H2O. The ability of this compound to destroy E. coli and oxidize methylic orange under visible light was compared with those of other reference photocatalysts. Ag/AgBr/WO3·H2O is a highly efficient photocatalyst under visible light. The Ag/AgBr/WO3·H2O samples recovered from repeated photooxidation experiments are almost identical to the as-prepared samples, proving th...
311 citations
TL;DR: Combining the versatility of the electrospinning technique and hydrothermal growth of nanostructures enabled the fabrication of hierarchical SnO(2)/TiO( 2) composite nanostructure that showed enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the bare TiO (2) nanofibers under UV light irradiation.
Abstract: Combining the versatility of the electrospinning technique and hydrothermal growth of nanostructures enabled the fabrication of hierarchical SnO2/TiO2 composite nanostructures The results revealed that not only were secondary SnO2 nanostructures successfully grown on primary TiO2 nanofiber substrates but also the SnO2 nanostructures were uniformly distributed without aggregation on TiO2 nanofibers By adjusting fabrication parameters, the morphology as well as coverage density of secondary SnO2 nanostructures could be further controlled, and then SnO2/TiO2 heterostructures with SnO2 nanoparticles or nanorods were facilely fabricated The photocatalytic studies suggested that the SnO2/TiO2 heterostructures showed enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the bare TiO2 nanofibers under UV light irradiation
308 citations
TL;DR: A new porous coordination polymer Cu[Cu(pdt)2], which shows relatively high electrical conductivity by the introduction of electron donors and acceptors as building units and forms a triangular spin lattice and shows spin frustration.
Abstract: We synthesized a new porous coordination polymer Cu[Cu(pdt)2], which shows relatively high electrical conductivity (6 × 10−4 S cm−1 at 300 K) by the introduction of electron donors and acceptors as building units. This compound is applicable as a porous electrode with high power density. In addition, this compound forms a triangular spin lattice and shows spin frustration.
284 citations
TL;DR: Three 3D lanthanide anionic metal-organic frameworks synthesized under hydrothermal conditions with 1D channels increased significantly upon the addition of Ca(2+) ions, while the introduction of other metal ions caused the intensities to be either unchanged or weakened.
Abstract: Three 3D lanthanide anionic metal−organic frameworks {K5[Ln5(IDC)4(ox)4]}n·(20H2O)n with 1D channels were synthesized under hydrothermal conditions [Ln = Gd (1), Tb (2), and Dy (3)]. The K+ ions within the 1D channel are easily exchanged with various cations. The emission intensities of TbIII in 2 increased significantly upon the addition of Ca2+ ions, while the introduction of other metal ions caused the intensities to be either unchanged or weakened.
TL;DR: The differences in the metal-btre bridging mode and the btre ligand symmetry can be correlated with different signal patterns in the 13C cross polarization magic angle spinning (CPMAS) NMR spectra.
Abstract: Hydrothermal reactions of 1,2-bis(1,2,4-triazol-4-yl)ethane (btre) with copper(II), zinc(II), and cadmium(II) salts have yielded the dinuclear complexes [Zn2Cl4(μ2-btre)2] (1) and [Zn2Br4(μ2-btre)2] (2), the one-dimensional coordination polymer ∞1[Zn(NCS)2(μ2-btre)] (3), the two-dimensional networks ∞2[Cu2(μ2-Cl)2(μ4-btre)] (4), ∞2[Cu2(μ2-Br)2(μ4-btre)] (5), and ∞2{[Cd6(μ3-OH)2(μ3-SO4)4(μ4-btre)3(H2O)6](SO4)·∼6H2O} (6), and the three-dimensional frameworks ∞3{[Cu(μ4-btre)]ClO4·∼0.25H2O} (7), ∞3{[Zn(μ4-btre)(μ2-btre)](ClO4)2} (8), ∞3{[Cd(μ4-btre)(μ2-btre)](ClO4)2} (9), and ∞3[Cu2(μ2-CN)2(μ4-btre)] (10, 2-fold 3D interpenetrated framework). The copper-containing products 4, 5, 7, and 10 contain the metal in the +1 oxidation state, from a simultaneous redox and self-assembly reaction of the Cu(II) starting materials. The cyanide-containing framework 10 has captured the CN− ions from the oxidative btre decomposition. The perchlorate frameworks 7, 8, or 9 react in an aqueous NH4+PF6− solution with formation of...
TL;DR: Interestingly, complex 4 interacts with DNA more strongly than all of the other complexes through partial intercalation of the extended planar ring of dpq with DNA base stack, which suggests the involvement of 5,6-dimethyl groups on the phen ring in hydrophobic interaction with DNA surface.
Abstract: The mononuclear mixed ligand copper(II) complexes of the type [Cu(l-tyr)(diimine)](ClO4), where tyr is l-tyrosine and diimine is 2,2′-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), 5,6-dimet...
TL;DR: Two new metal-organic frameworks (MOFs) that have structures isoreticular to reported MOFs that use 1,4-benzenedicarboxylic acid (BDC) as a building block are constructed and NH(2)-BDC can be used as a surrogate for BDC in a number of MOFs thereby providing a handle for postsynthetic modification.
Abstract: 2-Amino-1,4-benzenedicarboxylic acid (NH2−BDC) has been found to be a compatible building block for the construction of two new metal-organic frameworks (MOFs) that have structures isoreticular to reported MOFs that use 1,4-benzenedicarboxylic acid (BDC) as a building block. DMOF-1-NH2 (DABCO MOF-1-NH2) is a derivative of a previously studied MOF that contains two-dimensional square grids based on NH2−BDC and zinc(II) paddle-wheel units; the grid layers are connected by DABCO (1,4-diazabicyclo[2.2.2]octane) molecules that coordinate in the axial positions of the paddlewheel secondary-building units (SBUs). UMCM-1-NH2 is an NH2−BDC derivative of UMCM-1 (University of Michigan Crystalline Material-1), a highly porous MOF reported by Matzger et al., and consists of both NH2−BDC and BTB (BTB = 4,4′,4′′-benzene-1,3,5-triyl-tribenzoate) linkers with Zn4O SBUs. The structure of UMCM-1-NH2 was confirmed by single-crystal X-ray diffraction. By using NH2−BDC to generate these MOFs, the pendant amino groups can serv...
TL;DR: The effects of replacing a single polypyridyl ligand with an analogous anionic cyclometalating ligand were investigated for a set of three structurally related series of Ru(II) compounds and it is determined that the thermodynamic potentials of many of these compounds are appropriate for conventional photoelectrochemical cells that utilize a titania electrode and iodide-based electrolyte.
Abstract: The effects of replacing a single polypyridyl ligand with an analogous anionic cyclometalating ligand were investigated for a set of three structurally related series of Ru(II) compounds formulated as [Ru(bpy)2(L)]z, [Ru(tpy)(L)]z, and [Ru(tpy)(L)Cl]z, where z = 0, +1, or +2, and L = polypyridyl (e.g., bpy = 2,2′-bipyridine, tpy = 2,2′:6′,2′′-terpyridine) or cyclometalating ligand (e.g., deprotonated forms of 2-phenylpyridine or 3−(2−pyridinyl)-benzoic acid). Each of the complexes were synthesized and characterized by 1H NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and/or elemental analyses (EA). Cyclic voltammetry reveals that cyclometalation causes a shift of the first oxidation and reduction potentials by −0.5 to −0.8 V and −0.2 to −0.4 V, respectively, relative to their polypyridyl congeners. These disparate shifts have the effect of inducing a bathochromic shift of the lowest-energy absorption bands by as much as 90 nm. With the aid of time-dependent density functional theory...
TL;DR: The unique physicochemical properties associated with the copresence of 3DOM and mesoporous walls make these porous materials ideal candidates for applications in heterogeneous catalysis and CO(2) adsorption.
Abstract: Three-dimensionally (3D) ordered macroporous (3DOM) MgO, gamma-Al(2)O(3), Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) with polycrystalline mesoporous walls have been successfully fabricated with the triblock copolymer EO(106)PO(70)EO(106) (Pluronic F127) and regularly packed monodispersive polymethyl methacrylate (PMMA) microspheres as the template and magnesium, aluminum, cerium and zirconium nitrate(s), or aluminum isopropoxide as the metal source. The as-synthesized metal oxides were characterized by means of techniques such as X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), Fourier transform infrared (FT-IR), high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy/selected area electron diffraction (HRTEM/SAED), BET, carbon dioxide temperature-programmed desorption (CO(2)-TPD), and hydrogen temperature-programmed reduction (H(2)-TPR). It is shown that the as-fabricated MgO, gamma-Al(2)O(3), Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) samples possessed single-phase polycrystalline structures and displayed a 3DOM architecture; the MgO, Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) samples exhibited worm-hole-like mesoporous walls, whereas the gamma-Al(2)O(3) samples exhibited 3D ordered mesoporous walls. The solvent (ethanol or water) nature and concentration, metal precursor, surfactant, and drying condition have an important impact on the pore structure and surface area of the final product. The introduction of surfactant F127 to the synthesis system could significantly enhance the surface areas of the 3DOM metal oxides. With PMMA and F127 in a 40% ethanol solution, one can generate well-arrayed 3DOM MgO with a surface area of 243 m(2)/g and 3DOM Ce(0.6)Zr(0.4)O(2) with a surface area of 100 m(2)/g; with PMMA and F127 in an ethanol-HNO(3) solution, one can obtain 3DOM gamma-Al(2)O(3)with a surface area of 145 m(2)/g. The 3DOM MgO and 3DOM gamma-Al(2)O(3) samples showed excellent CO(2) adsorption behaviors, whereas the 3DOM Ce(0.6)Zr(0.4)O(2) sample exhibited exceptional low-temperature reducibility. The unique physicochemical properties associated with the copresence of 3DOM and mesoporous walls make these porous materials ideal candidates for applications in heterogeneous catalysis and CO(2) adsorption.
TL;DR: The thermal stabilities and X-ray powder diffraction studies indicate that the framework of 3 can keep stable after the loss of guest molecules, and studies of the magnetic susceptibilities of 2-6 reveal weak antiferromagnetic exchange interactions between adjacent Co(II) centers.
Abstract: A series of interesting Co(II)−H2tbip coordination polymers incorporating different auxiliary ligands, {[Co(tbip)(bipy)(H2O)3]·0.5(bipy)·H2O}n (1), [Co(tbip)(bipy)]n (2), {[Co3(tbip)3(dpe)3]·0.5(dpe)·3H2O}n (3), [Co2(tbip)2(dpe)(H2O)]n (4), [Co2(tbip)2(bpa)(H2O)]n (5), and {[Co2(tbip)2(bpa)2]·2.5H2O}n (6) (H2tbip = 5-tert-butyl isophthalic acid; bipy = 4,4′-bipyridine; dpe = 1,2-di (4-pyridyl)ethylene; bpa = 1,2-bi(4-pyridyl)ethane) were synthesized. X-ray structural analyses of 1−6 reveal a diverse range of structures, ranging from 1D (1) to 2D (2, 6) to 3D (3, 4, 5). Complex 1 shows 1D zigzag bipy-bridged polymeric chains with the terminal tbip ligands as pendants, which are extended to a 3D hydrogen-bonded supramolecular framework involving 1D open channels which encapsulate guest bipy molecules. Polymers 2 and 6 feature similar 2D infinite layer frameworks consisting of cobalt dimers. The structure of 3 is constructed from [Co2(tbip)2]n layers, which consists of alternating left- and right-handed heli...
TL;DR: Topology analysis reveals that complexes I an V represent rare (4,8)-connected flu and (3,4)-connected zeolite-like nets, respectively, and the diversity in inorganic arrays leads to differences in luminescent properties of these complexes.
Abstract: The hydro(solvo)thermal reactions of Pb(OAc)2·3H2O with the aromatic carboxylic ligands 1,3,5-benzenetricarboxylic and 1,4-, 1,2-, and 1,3-benzenedicarboxylic acids (1,3,5-H3BTC; 1,4-, 1,2-, and 1,3-H2BDC) have yielded a family of inorganic−organic framework materials: [Pb2(1,3,5-BTC)(μ3-OH)(H2O)]n (Ι), [NaPb(1,3,5-BTC)(H2O)]n (ΙΙ), [Pb(1,4-BDC)]n (ΙΙΙ), [Pb5(1,2-BDC)4(OAc)2]n (IV), and {[Pb5(1,3-BDC)5(H2O)2]2·H2O}n (V). These complexes have been characterized by means of single-crystal X-ray diffraction, X-ray powder diffraction, thermogravimetric analysis−mass spectrometry, and photoluminescence spectra. They are all three-dimensional structures except for two-dimensional IV. Topology analysis reveals that complexes I an V represent rare (4,8)-connected flu and (3,4)-connected zeolite-like nets, respectively. The five complexes exhibit diverse inorganic connectivity, including a 0D Pb4O16 cluster for I, a 1D Pb−O−Pb chain for II, a 2D Pb−O−Pb network for III and IV, and an unprecedented 3D Pb−O−Pb frame...
TL;DR: Five density functionals were calibrated for the prediction of 57Fe Mössbauer isomer shifts on a set of 20 iron-containing molecules and the influence of scalar relativistic effects and the basis set dependence of the predictions were investigated.
Abstract: Five density functionals including GGA (generalized gradient approximation) (BP86), meta-GGA (TPSS), hybrid meta-GGA (TPSSh), hybrid (B3LYP), and double-hybrid functionals (B2PLYP) were calibrated for the prediction of 57Fe Mossbauer isomer shifts on a set of 20 iron-containing molecules. The influence of scalar relativistic effects and the basis set dependence of the predictions were investigated.
TL;DR: The photocatalytic property of as-synthesized hierarchical FeWO4 microcrystals has been first studied in this paper, which shows excellent photocatalysis activity for the degradation of rhodamine B (RhB) under UV and visible light irradiation.
Abstract: Highly hierarchical platelike FeWO4 microcrystals have been synthesized by a simple solvothermal route using FeCl3·6H2O and Na2WO4·2H2O as precursors, where ethylene glycol (EG) plays an important role as a capping agent in directing growth and self-assembly of such unique structures. In addition, a certain amount of CH3COONa (NaAc) was necessary for the formation of such unique FeWO4 microstructures. The photocatalytic property of as-synthesized hierarchical FeWO4 microcrystals has been first studied, which shows excellent photocatalytic activity for the degradation of rhodamine B (RhB) under UV and visible light irradiation (modeling sunlight). Moreover, magnetic measurement indicates that hexangular FeWO4 platelike microcrystals show a small ferromagnetic ordering at low temperature because of spin-canting of antiferromagnetic materials and surface spins of FeWO4 nanoparticles.
TL;DR: The results show that a variety of functional groups can be introduced onto the MOF including amines, carboxylic acids, and chiral groups, and it is shown that tert-butyl-based asymmetric anhydrides can be used to selectively deliver chemical payloads to the IRMOF.
Abstract: An isoreticular metal-organic framework (IRMOF-3) containing 2-amino-1,4-benzenedicarboxylic acid (NH2−BDC) as a building block is shown to undergo chemical modification with a diverse series of anhydrides and isocyanates. The modification of IRMOF-3 by these reagents has been evidenced by using a variety of methods, including NMR and electrospray ionization mass spectrometry, and the structural integrity of the modified MOFs has been confirmed by thermogravimetric analysis, powder X-ray diffraction, and gas sorption analysis. The results show that a variety of functional groups can be introduced onto the MOF including amines, carboxylic acids, and chiral groups. Furthermore, it is shown that tert-butyl-based asymmetric anhydrides can be used to selectively deliver chemical payloads to the IRMOF. Finally, the results demonstrate that at least four different chemical modifications can be performed on IRMOF-3 and that the reaction conditions can be modulated to control the relative abundance of each group. ...
TL;DR: The present contribution gives a definition of the phenomenon, a process that changes the magnetism of a (molecular) system after absorption of a photon, limited to the discussion of photomagnetism based on metal-metal electron transfer in clusters and extended molecule-based magnets.
Abstract: Photomagnetism in molecular systems is a new development in molecular magnetism. It traces back to 1982 and 1984 when a transient effect and then the light-induced excited-spin-state-trapping effect was discovered in spin-crossover complexes. The present contribution gives a definition of the phenomenon, a process that changes the magnetism of a (molecular) system after absorption of a photon. It is limited to the discussion of photomagnetism based on metal−metal electron transfer in clusters and extended molecule-based magnets. The paper is organized around the main pairs of spin bearers, which allowed us to evidence and to study the phenomenon: Cu−Mo, Co−Fe, and Co−W. For each metallic pair, we report and discuss the conditions of appearance of the effect and its characteristics, both in extended structures and in molecular units: structure, spectroscopy, magnetism, thermodynamics and kinetics, and applications. We conclude with some brief prospects. The field is in rapid expansion. We are convinced tha...
TL;DR: A modified Kurtz nonlinear optical powder technique was used to determine the SHG responses of both compounds, and Li(2)CdSnS(4) displayed a type I phase-matchable response of approximately 70x alpha-quartz, while Li
Abstract: The semiconductors Li(2)CdGeS(4) and Li(2)CdSnS(4), which are of interest for their nonlinear optical properties, were synthesized using high-temperature solid-state and polychalcogenide flux syntheses. Both compounds were found to crystallize in Pmn2(1), with R1 (for all data) = 1.93% and 1.86% for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively. The structures of both compounds are diamond-like with the tetrahedra pointing in the same direction along the c axis. The alignment of the tetrahedra results in the structure lacking an inversion center, a prerequisite for second-harmonic generation (SHG). A modified Kurtz nonlinear optical powder technique was used to determine the SHG responses of both compounds. Li(2)CdGeS(4) displayed a type I phase-matchable response of approximately 70x alpha-quartz, while Li(2)CdSnS(4) displayed a type I non-phase-matchable response of approximately 100x alpha-quartz. Diffuse-reflectance spectroscopy was used to determine band gaps of 3.10 and 3.26 eV for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively.
TL;DR: Four microporous lanthanide metal-organic frameworks (MOFs) with coordinatively linked doubly interpenetrated (8,3)-connected nets exhibit interesting photoluminescence phenomena and are isostructural, which also reflects the lanthanides' contraction trend.
Abstract: Under solvothermal conditions, the reactions of trigonal-planar ligand, TATB (4,4′,4′′-s-triazine-2,4,6-triyl-tribenzoate) with Dy(NO3)3, Er(NO3)3, Y(NO3)3, Yb(NO3)3, gave rise to four microporous lanthanide metal-organic frameworks (MOFs), designated as PCN-17 (Dy), PCN-17 (Er), PCN-17 (Y), and PCN-17 (Yb), respectively. The four porous MOFs are isostructural, with their crystal unit parameters shrinking in the order of PCN-17 (Dy), PCN-17 (Y), PCN-17 (Er), and PCN-17 (Yb), which also reflects the lanthanides' contraction trend. All of them adopt the novel square-planar Ln4(μ4-H2O) cluster as the secondary building unit and contain coordinatively linked doubly interpenetrated (8,3)-connected nets. In addition to exhibiting interesting photoluminescence phenomena, the coordinatively linked interpenetration restricts the pore sizes and affords them selective adsorption of H2 and O2 over N2 and CO, as well as renders them with high thermal stability of 500−550 °C as demonstrated from TGA profiles.
TL;DR: Comparison with literature data suggests that the activation entropies might be used as indicators distinguishing between heterolytic and homolytic cleavage of the peroxo bond in the redox reactions of HSO(5)(-).
Abstract: The kinetics of the redox reactions of the peroxomonosulfate ion (HSO(5)(-)) with iron(II), vanadium(IV), cerium(III), chloride, bromide, and iodide ions were studied. Cerium(III) is only oxidized upon illumination by UV light and cerium(IV) is produced in a photoreaction with a quantum yield of 0.33 +/- 0.03. Iron(II) and vanadium(IV) are most probably oxidized through one-electron transfer producing sulfate ion radicals as intermediates. The halide ions are oxidized in a formally two-electron process, which most likely includes oxygen-atom transfer. Comparison with literature data suggests that the activation entropies might be used as indicators distinguishing between heterolytic and homolytic cleavage of the peroxo bond in the redox reactions of HSO(5)(-).
TL;DR: It was demonstrated that the titanate nanotubes consist of two-dimensional TiO(6) octahedral host layers with a lepidocrocite (gamma-FeOOH)-type layered structure.
Abstract: Crystal structures of titanate nanotubes prepared from a NaOH treatment of TiO2 with subsequent acid washing were discussed from a viewpoint of vibrational spectroscopy. The correlation between the vibrational feature and the polymerization nature of the TiO6 octahedron was established by analyzing Raman scattering data of crystalline TiO2 (anatase and rutile) and layered protonic titanates. Then, the polymerization nature of TiO6 octahedra in the titanate nanotubes was identified by comparing their Raman scattering spectra with those of the crystalline TiO2 and layered protonic titanates. It demonstrated that the titanate nanotubes consist of two-dimensional TiO6 octahedral host layers with a lepidocrocite (γ-FeOOH)-type layered structure. This conclusion was confirmed further by considering the Raman scattering properties of a restacked titanate prepared by assembling TiO6 octahedral layers derived from the original scroll-like titanate nanotubes. Our findings offered a convenient approach to validate t...
TL;DR: A blue phosphorescent iridium(III) complex bearing fluorine-substituted bipyridine (dfpypy) has been synthesized and characterized to investigate the effect of the substitution and replacement of the phenyl ring in ppy with pyridine on the solid state structure and its photoluminescence.
Abstract: A blue phosphorescent iridium(III) complex (1) bearing fluorine-substituted bipyridine (dfpypy) has been synthesized and characterized to investigate the effect of the substitution and replacement of the phenyl ring in ppy (phenylpyridine) with pyridine on the solid state structure and its photoluminescence. The optical properties and electrochemical behaviors of 1 have also been systematically evaluated. The structure of 1 has also been determined by a single-crystal X-ray diffraction analysis. There are varied intermolecular interactions caused by the pyridine and fluorine substituents, such as C−H···N, C−H···F, and π···π interactions of either face-to-face type or edge-to-face C−H···π and halogen···π in crystal packing. In electrochemistry, the remarkably higher oxidation potential than that of FIrpic was observed. The emission λmax of 1 at room temperature is at 438 nm with a higher PL quantum efficiency. Complex 1 exhibits intense blue emission with high color purity (CIE x = 0.14, y = 0.12), which h...
TL;DR: It was found that the addition of CTAB can adjust the morphologies of BiVO(4) and obstruct the crystal phase transformation from the mixed crystal to pure monoclinic BiVO (4) during the hydrothermal process.
Abstract: Microspheric and lamellar BiVO4 powders were selectively prepared through a hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as a template-directing reagent. The as-prepared BiVO4 powders were characterized by X-ray diffraction, electron microscopy, nitrogen adsorption−desorption experimentation, Fourier transform infrared spectrometry, and UV−vis diffuse reflectance spectroscopy. Experimental results indicate that microspheric BiVO4 with particle sizes in the range of 7∼12 μm can be derived from a relatively low hydrothermal temperature (≤160 °C) and possess a mixed crystal consisting of tetragonal and monoclinic phases, whereas lamellar BiVO4 with a pure monoclinic phase can be obtained at a higher hydrothermal temperature (200 °C). Their photocatalytic activities for O2 evolution were investigated by using Fe(NO3)3 as a sacrificial reagent under visible-light irradiation, and the lamellar BiVO4 shows a better photoactivity than the microspheric product due to its pure monoclinic crys...
TL;DR: CMP:Eu(2+),Mn(2+) could be regarded as a good candidate for UV LED-based white LEDs based on the luminescence spectra, energy transfer efficiency, and decay curve of the phosphors.
Abstract: On the basis of the structural information that the host material has excellent charge stabilization, blue-emitting Ca6−x−yMgx(PO4)4:Euy2+ (CMP:Eu2+) phosphors were synthesized and systematically optimized, and their photoluminescence (PL) properties were evaluated. Depending upon the amount of Mg added, the emission efficiency of the phosphors could be enhanced. The substitution of Eu2+ affected their maximum wavelength (λmax) and thermal stability because the substitution site of Eu2+ could be varied. To obtain single-phase two-color-emitting phosphors, we incorporated Mn2+ into CMP:Eu2+ phosphors. Weak red emission resulting from the forbidden transition of Mn2+ could be enhanced by the energy transfer from Eu2+ to Mn2+ that occurs because of the spectral overlap between the photoluminescence excitation (PLE) spectrum of Mn2+ and the PL spectrum of Eu2+. The energy transfer process was confirmed by the luminescence spectra, energy transfer efficiency, and decay curve of the phosphors. Finally, the opti...
TL;DR: The V-Salen and V-salan complexes show higher activity and normally better selectivity in alkene oxidation and higherActivity and enantioselectivity for sulfoxidation than their parent V- salen complexes, therefore being an advantageous alternative ligand system for oxidation catalysis.
Abstract: We report the synthesis and characterization of several chiral salen- and salan-type ligands and their vanadium complexes, which are derived from salicylaldehyde or salicylaldehyde derivatives and chiral diamines (1R,2R-diaminocyclohexane, 1S,2S-diaminocyclohexane, and 1S,2S-diphenylethylenediamine). The structures of H2sal(R,R-chan)2+·2Cl−·(CH3)2CHOH·H2O (1c; H2sal(R,R-chan) = N,N′-salicyl-R,R-cyclohexanediaminium), Etvan(S,S-chen) (3c; Etvan(S,S-chen) = N,N′-3-ethoxy-salicylidene-S,S-cyclohexanediiminato), and naph(R,R-chen) (6c; naph(R,R-chen) = N,N′-naphthylidene-R,R-cyclohexanediiminato) were determined by single-crystal X-ray diffraction. The corresponding vanadium(IV) complexes and several other new complexes involving different salicylaldehyde-type precursors were prepared and characterized in the solid state and in solution by spectroscopic techniques: UV−vis, circular dichroism, electron paramagnetic resonance, and 51V NMR, which provide information on the coordination geometry. The salan comple...