Design and synthesis of heterobimetallic donor-acceptor chemodosimetric ensembles for the detection of sulfhydryl-containing amino acids and peptides

A competitive indicator displacement assay has been successfully developed for the ratiometric determination of sulfhydryl-containing amino acids and peptides using heterobimetallic donor-acceptor complexes as chemodosimetric ensembles. Chromotropic cis-[ML2(CN)2](M = FeII, RuII, OsII; L = diimine) are used as signaling indicators and PtII(DMSO)Cl2 acceptor moiety is used as the receptor for the sulfhydryl-containing analytes. A series of three heterobimetallic donor-acceptor complexes: cis-FeII(bpy)2[CN-PtII(DMSO)Cl2]2 (1), cis-Ru(II)(bpy)2[CN-PtII(DMSO)Cl2]2 (2) and cis-Os(II)(bpy)2[CN-PtII(DMSO)Cl2]2 (3) are synthesized and characterized by X-ray crystallography. All the three ensembles are able to produce specific colorimetric/fluorimetric responses to sulfhydryl-containing amino acids (cysteine, homocysteine and methionine) as well as the sulfhydryl-containing small peptide glutathione. The mechanism of the competitive displacement assay is evaluated by examining the thermodynamics of formation of the donor-acceptor linkage and adducts between the acceptor metal and the sulfhydryl-containing analytes as well as by systematic variation of the donor and acceptor metals in the chemodosimetric ensembles.     

Nature of the bottom t2g-block bands of layered perovskites. Implications for the transport properties of phases where these bands are partially filled

The electronic structure of a series of double layer (Sr(3)V(2)O(7), KLaNb(2)O(7), Li(2)SrNb(2)O(7), RbLaNb(2)O(7), Rb(2)LaNb(2)O(7)) as well as triple layer (Ca(4)Ti(3)O(10), K(2)La(2)Ti(3)O(10), Sr(4)V(3)O(9.7), CsCa(2)Nb(3)O(10)) Dion-Jacobson and Ruddlesden-Popper phases and quadruple layer A(n)()B(n)(O(3)(n)(+2) phases (Sr(2)Nb(2)O(7) as well as the low-temperature and room-temperature structures of Sr(2)Ta(2)O(7)) has been studied by means of a first-principles density functional theory approach. The results are rationalized on the basis of a simple tight-binding scheme, which provides a simple yet precise scheme allowing the correlation of the crystal structure details and the nature of the bottom t(2g)-block band levels. Both the quantitative and the qualitative approaches are used to analyze the nature of the carriers in intercalated samples of the d(0) semiconducting phases as well as those of the metallic d(x) (0 < x < or = 1) systems. The Ruddlesden-Popper and Dion-Jacobson materials with partially filled t(2g)-block bands must be genuine two-dimensional metals except when the M-O(ap) distances of the outer layer octahedra are similar and the band filling is not low. The conducting electrons in these phases are almost equally distributed among the different layers. It is shown that the A(n)()B(n)O(3)(n)(+2) phases with partially filled bands are potentially interesting materials because they are structurally two-dimensional materials exhibiting one-dimensional band structure features. Finally, the possible application of the simple scheme to related materials such as layered perovskite oxynitrides and the effect of disorder are briefly discussed.     

Synthesis, spectral, thermal and magnetic studies of Mn(II), Ni(II) and Cu(II) complexes with some benzopyran-4-one Schiff bases

The Schiff bases of N(2)O(2) dibasic ligands, H(2)La and H(2)Lb are prepared by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one. Also tetra basic ligands, H(4)La and H(4)Lb are prepared by the condensation of aliphatic amines (a) and (b) with 6-formyl-5,7-dihydroxy-2-methylbenzopyran-4-one. New complexes of H(4)La and H(4)Lb with metal ions Mn(II), Ni(II) and Cu(II) are synthesized, in addition Mn(II) complexes with ligands H(2)La and H(2)Lb are also synthesized. Elemental and thermal analyses, infrared, ultraviolet-visible as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. The structures of copper(II) complexes are also assigned based upon ESR spectra study. All the complexes separated with the stoichiometric ratio (1:1) (M:L) except Mn-H(4)La and Mn-H(4)Lb with (2:1) (M:L) molar ratio. In metal chelates of the type 1:1 (M:L), the Schiff bases behave as a dinegative N(2)O(2) tetradentate ligands. Moreover in 2:1 (M:L) complexes, the Schiff base molecules act as mono negative bidentate ligand and binuclear complex is then formed. The Schiff bases were assayed by the disc diffusion method for antibacterial activity against Staphylococcus aureus and Escherichia coli. The antifungal activity of the Schiff bases was also evaluated against the fungi Aspergillus flavus and Candida albicans.     

Fluorinated Metal–Organic Frameworks: Advantageous for Higher H2 and CO2 Adsorption or Not?

The synthesis, structure, and gas adsorption properties of three new metal-organic frameworks (MOFs) designed from isonicotinic acid (INA) and its fluorinated analogue 3-fluoroisonicotinic acid (FINA) along with Co(II) as the metal center have been reported. Co-INA-1 ([Co(3)(INA)(4)(O)(C(2)H(5)OH)(3)][NO(3)]·C(2)H(5)OH·3H(2)O; INA=isonicotinic acid) and Co-INA-2 ([Co(INA)(2)]·DMF) are structural isomers as are Co-FINA-1 ([Co(3-)(FINA)(4)(O)(C(2) H(5) OH)(2)]·H(2)O; FINA=3-fluoroisonicotinic acid) and Co-FINA-2 ([Co(FINA)(2)]·H(2)O), but the most important thing to note here is that Co-INA-1 and Co-FINA-1 are isostructural as are Co-INA-2 and Co-FINA-2. The effect of partial introduction of fluorine atoms into the framework on the gas uptake properties of MOFs having similar structures has been analyzed experimentally and computationally in isostructural MOFs.     

Addition of bromine chloride and iodine monochloride to carbonyl-conjugated, acetylenic ketones: synthesis and mechanisms

The reactions of 3-butyn-2-one (1), 3-hexyn-2-one (2), and 4-phenyl-3-butyn-2-one (3) with bromine chloride (BrCl) and iodine monochloride (ICl) in CH(2)Cl(2), CH(2)Cl(2)/pyridine, and MeOH are described. The data show that the major products in CH(2)Cl(2) are (Z)-AM (anti-Markovnikov) regioisomers. With the exception of 3 and ICl, the (E)-AM regioisomers predominate when pyridine was added as an acid scavenger. Minor amounts of the M regioisomers were formed with 1 and 2 and BrCl. The percentage of M regioisomer increased significantly with 1 and BrCl in MeOH, but MeOH had little affect on the other reactions. Isolation and stability of the products are discussed. Detailed evidence for the structures of the products, involving a combination of MS, (1)H and (13)C NMR, and IR, is presented; HRMS analyses are provided as proofs for all of the products. The acid-catalyzed mechanism and the halonium ion mechanism are considered as possible pathways in the formation of the products.     

Visible-light-sensitized production of hydrogen using perfluorosulfonate polymer-coated TiO2 nanoparticles: an alternative approach to sensitizer anchoring

TiO(2) sensitized by derivatized ruthenium bipyridyl complexes has been intensively investigated as a tool to utilize visible light. This article describes an alternative approach to attaching ruthenium complex sensitizers at the TiO(2)/H(2)O interface, which is a much simpler and more efficient way to produce hydrogen. The surface of TiO(2) particles are simply coated with perfluorosulfonate polymer (cation-exchange resin: Nafion), and then Ru(bpy)(3)(2+) (as a cationic form), whose bipyridyl ligands are not functionalized with carboxylic acid groups, are bound within the Nafion layer through electrostatic attraction. The visible-light-induced production of H(2) on Nf/TiO(2) using simple Ru(bpy)(3)(2+) as a sensitizer is far more efficient than that on Ru(dcbpy)(3)-TiO(2), upon which many sensitized photoelectrochemical conversion systems are based. Effects of various experimental parameters such as pH, concentration of Ru(bpy)(3)(2+), Nafion loading, and the kind of TiO(2) were investigated. Under optimized conditions, the H(2) production rate was about 80 mumol/h, which corresponds to an apparent photonic efficiency of 2.6%. The roles of the Nafion layer on TiO(2) in the sensitized H(2) production are proposed to be twofold: to provide binding sites for cationic sensitizers and to enhance the local activity of protons in the surface region.     

Theoretical study of the electronic structure of MCH(2)(+)(M=Fe,Co,Ni)

State of the art coupled cluster (CC) methods are applied to accurately characterize the ground state electronic structure and photoelectron spectra of transition metal carbene ions MCH(2) (+) (M=Fe, Co, and Ni). The geometries and energies of the lowest energy quartet, triplet, and doublet electronic states as well as several low-lying vertical excitation energies of FeCH(2) (+), CoCH(2) (+), and NiCH(2) (+) are reported. The excitation energies are computed using the equation-of-motion CC and for states of different symmetries, by the energy differences of single reference ground and excited states (Delta-CC). The latter employ several reference states; the unrestricted Hartree-Fock, restricted open shell Hartree-Fock, and unrestricted Kohn-Sham. We conclude that the (2)A(1) electronic ground state of NiCH(2) (+) is separated by about 30.0 kJ/mol from the next highest state, and the lowest (4)B(1) and (4)B(2) states of FeCH(2) (+) as well as the (3)A(2) and (3)A(1) states of CoCH(2) (+) are nearly degenerate. The presence of metal-pi*(MCH(2)) charge transfer states with significant oscillator strengths in the visible/near-UV energy domain of the theoretical spectra of FeCH(2) (+) and CoCH(2) (+) are at the origin of the photofragmentation of these compounds observed after irradiation between 310 and 360 nm.     

Why are proton transfers at carbon slow? Self-exchange reactions

When the quantum character of proton transfer is taken into account, the intrinsic slowness of self-exchange proton transfer at carbon appears as a result of its nonadiabatic character as opposed to the adiabatic character of proton transfer at oxygen and nitrogen. This difference is caused by the lesser polarity of C-H bonds as compared to that of O-H and N-H bonds. Besides solvent and heavy-atom intramolecular reorganizations, the kinetics of the reaction are consequently governed at the level of a pre-exponential term by proton tunneling through the barrier. These contrasting behaviors are illustrated by an analysis of the CH(3)H + (-)CH(3), H(2)O + OH(-), and (+)NH(4) + NH(3) self-exchange reactions. The effect of electron-withdrawing substituents and the case of cation radicals are discussed within the same framework taking the O(2)NCH(2)H + CH(2)=NO(2)(-) and (+.)H(2)NCH(2)H + (.)CH(2)NH(2) as examples. Illustrated by the CH(2)=CH-CH(2)H + (-)CH(2)-CH=CH(2) couple, it is shown that the "imbalanced character of the transition state" is related to heavy-atom intramolecular reorganization. Combination of these various effects is finally analyzed, taking the O(2)N-CH(2)=CH-CH(2)H + CH(2)=CH-CH=NO(2)(-) and (+.)H(2)N-CH(2)=CH-CH(2)H + (.)CH(2)-CH=CH(2)-NH(2) couples as examples.     

New metal complexes with diclofenac containing 2-pyridineethanol or 2-pyridinepropanol: synthesis,structural, spectroscopic,thermal properties,catechol oxidase and carbonic anhydrase activities

Four new neutral diclofenac-based complexes, [Co(dicl)2(2-pyet)2] 1, [Ni(dicl)2(2-pyet)2] 2, [Cu2(dicl)2(2-pyet)2] 3, and [Cu2(dicl)2(2-pypr)2] 4 have been synthesized and characterized by elemental analysis, FT-IR, thermal analysis. Complexes 1, 3, and 4 have also been characterized by X-ray single-crystal structural analysis. The compounds of Co(II) and Ni(II) have octahedral geometry with two diclofenac and two 2-pyridineethanol ligands in the coordination sphere. The compounds of Cu(II) have square-pyramidal geometry and Cu(II) ions are linked via oxygens to the bridging 2-pyridineethanol or 2-pyridinepropanol ligands. The Δν values acquired by FT-IR are in agreement with the single XRD data. Studies on the thermal properties are reported and the complexes are stable to 196, 216, 215, and 201 °C in air, respectively. Two dinuclear Cu(II) complexes have demonstrated catalytic activity on oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone showing saturation kinetics at high substrate concentrations. The diclofenac complexes are investigated as inhibitors of the human cytosolic isoforms hCA I and II. The complexes are good as hCA I inhibitors (Kis of 1.52–55.06 μM) but only moderately efficient as hCA II inhibitors (Kis of 0.23–5.61 μM).     

Formation of organolithium hetero-aggregates [Li4Ar2(nBu)2] (Ar=C6H4CH(Me)NMe2-2) during the directed ortho-lithiation of [1-(dimethylamino)ethyl]benzene

(R)-[1-(Dimethylamino)ethyl]benzene reacts with nBuLi in a 1:1 molar ratio in pentane to quantitatively yield a unique hetero-aggregate (2 a) containing the lithiated arene, unreacted nBuLi, and the complexed parent arene in a 1:1:1 ratio. As a model compound, [Li(4)(C(6)H(4)CH(Me)NMe(2)-2)(2)(nBu)(2)] (2 b) was prepared from the quantitative redistribution reaction of the parent lithiated arene Li(C(6)H(4)CH(Me)NMe(2)-2) with nBuLi in a 1:1 molar ratio. The mono-Et(2)O adduct [Li(4)(C(6)H(4)CH(Me)NMe(2)-2)(2)(nBu)(2)(OEt(2))] (2 c) and the bis-Et(2)O adduct [Li(4)(C(6)H(4)CH(Me)NMe(2)-2)(2)(nBu)(2)(OEt(2))(2)] (2 d) were obtained by re-crystallization of 2 b from pentane/Et(2)O and pure Et(2)O, respectively. The single-crystal X-ray structure determinations of 2 b-d show that the overall structural motifs of all three derivatives are closely related. They are all tetranuclear Li aggregates in which the four Li atoms are arranged in an almost regular tetrahedron. These structures can be described as consisting of two linked dimeric units: one Li(2)Ar(2) dimer and a hypothetical Li(2)nBu(2) dimer. The stereochemical aspects of the chiral Li(2)Ar(2) fragment are discussed. The structures as observed in the solid state are apparently retained in solution as revealed by a combination of cryoscopy and (1)H, (13)C, and (6)Li NMR spectroscopy.     

Effect of temperature on pseudoternary system Tween-80-butanol-hexane-water

Novel periodic mesostructured organometallic silicas of MCM-41 type bearing homogeneously distributed bis(8-quinolinolato)dioxomolybdenum(VI) inside the channel walls (denoted as MoO(2)Q(2)@PMO-x) are synthesized via a convenient one-pot method and examined as catalysts in the epoxidation of cyclooctene. The ordered mesoporous structures as well as the organometallic groups incorporated into the framework are fully determined by comprehensive characterization techniques such as XRD, TEM, N(2) adsorption/desorption, SEM, FT-IR, UV-vis spectroscopy, solid-state NMR, ICP-AES, XPS and TG/DSC. MoO(2)Q(2)@PMO-6% catalyst exhibits higher activity for the epoxidation of cyclooctene with tert-butyl hydroperoxide than other MoO(2)Q(2)@PMO materials and its homogeneous or randomly grafted analogue.     

Synthesis, structure, and characterization of new mononuclear Mn(II) complexes. Electrochemical conversion into new oxo-bridged Mn(2)(III,IV) complexes. Role of chloride ions

Two Mn(II) complexes are isolated and X-ray characterized, namely, cis-[(L(2))Mn(II)(Cl)(2)] (1) and [(L(3))Mn(II)Cl(OH(2))](ClO(4)) (2(ClO(4))), where L(2) and L(3) are the well-known tetradentate N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine and N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)propane-1,3-diamine ligands, respectively. The crystal structure reveals that whereas the ligand L(2) is in the cis-alpha conformation in complex 1, the ligand L(3) is in the more unusual cis-beta conformation in 2. EPR spectra are recorded on frozen solutions for both complexes and are characteristic of Mn(II) species. Electrochemical behaviors are investigated on acetonitrile solution for both complexes and show that cation 2 exists as closely related Mn(II) species in equilibrium. For both complexes exhaustive bulk electrolyses of acetonitrile solution are performed at oxidative potential in various experimental conditions. In the presence of 2,6-lutidine and after elimination of chloride ligands, the formation of the di-mu-oxo mixed-valent complexes [(L(2))Mn(III)(mu-O)(2)Mn(IV)(L(2))](3+) (3a) and [(L(3))Mn(III)(mu-O)(2)Mn(IV)(L(3))](3+) (4) is confirmed by UV-vis and EPR spectroscopies and cyclic voltammetry. In addition crystals of 4(ClO(4))(3) were isolated, and the X-ray structure reveals the cis-alphaconformation of L(3). In the absence of 2,6-lutidine and without elimination of the exogenous chloride ions, the electrochemical oxidation of 1 leads to the formation of the mononuclear Mn(III) complex, namely, [(L(2))Mn(III)(Cl)(2)](+) (5), as confirmed by UV-vis as well as parallel mode EPR spectroscopy and cyclic voltammetry. In the same conditions, the electrochemical oxidation of complex 2 is more intricate, and a thorough analysis of EPR spectra establishes the formation of the binuclear mono-mu-oxo mixed-valent [(L(3))ClMn(III)(mu-O)Mn(IV)Cl(L(3))](3+) (6) complexes. Electrochemical conversion of Mn(II) complexes into mixed-valent Mn(2)(III,IV) oxo-bridged complexes in the presence of 2,6-lutidine is discussed. The role of the chloride ligands as well as that of L(3) in the building of oxo bridges is discussed. Differences in behavior between L(2) and L(3) are commented on.     

Influence of the cation size on the framework structures and space group centricities in AMo2O5(SeO3)2 (A = Sr, Pb, and Ba)

Two new quaternary mixed-metal selenites, SrMo(2)O(5)(SeO(3))(2) and PbMo(2)O(5)(SeO(3))(2), have been synthesized as crystals and pure polycrystalline phases by standard solid-state reactions using SrMoO(4), PbO, MoO(3), and SeO(2) as reagents. The crystal structures of the reported materials have been determined by single-crystal X-ray diffraction. SrMo(2)O(5)(SeO(3))(2) and PbMo(2)O(5)(SeO(3))(2) are isostructural and crystallized in the triclinic centrosymmetric space group P1? (No. 2). The reported materials exhibit chain structures consisting of MoO(6) octahedra and asymmetric SeO(3) polyhedra. Complete characterizations including IR spectroscopy and thermal analyses for the compounds are also presented, as are dipole moment calculations. In addition, the powder second-harmonic-generating (SHG) properties of noncentrosymmetric polar BaMo(2)O(5)(SeO(3))(2) have been measured using 1064 nm radiation. Through powder SHG measurement, we are able to determine that BaMo(2)O(5)(SeO(3))(2) has a SHG efficiency of approximately 80 times that of α-SiO(2). Additional SHG measurements reveal that the material is phase-matchable (type 1). A detailed cation size effect on the symmetry and framework structure is discussed.     

Application of Gaussian-type geminals in local second-order Møller-Plesset perturbation theory

In this work Gaussian-type Geminals (GTGs) are applied in local second-order Moller-Plesset perturbation theory to improve the basis set convergence. Our implementation is based on the weak orthogonality functional of Szalewicz et al., [Chem. Phys. Lett. 91, 169 (1982); J. Chem. Phys. 78, 1420 (1983)] and a newly developed program for calculating the necessary many-electron integrals. The local approximations together with GTGs in the treatment of the correlation energy are introduced and tested. First results for correlation energies of H(2)O, CH(4), CO, C(2)H(2), C(2)H(4), H(2)CO, and N(2)H(4) as well as some reaction and activation energies are presented. More than 97% of the valence-shell correlation energy is recovered using aug-cc-pVDZ basis sets and six GTGs per electron pair. The results are compared with conventional calculations using correlation-consistent basis sets as well as with MP2-R12 results.     

Synthesis, structure, and thermal properties of soluble hydrazinium germanium(IV) and tin(IV) selenide salts

The crystal structures of two hydrazinium-based germanium(IV) and tin(IV) selenide salts are determined. (N(2)H(5))(4)Ge(2)Se(6) (1) [I4(1)cd, a = 12.708(1) Angstroms, c = 21.955(2) Angstroms, Z = 8] and (N(2)H(4))(3)(N(2)H(5))(4)Sn(2)Se(6) (2) [P, a = 6.6475(6) Angstroms, b = 9.5474(9) Angstroms, c = 9.8830(10) Angstroms, alpha = 94.110(2) degrees, beta = 99.429(2) degrees, gamma = 104.141(2) degrees, Z = 1] each consist of anionic dimers of edge-sharing metal selenide tetrahedra, M(2)Se(6)(4-) (M = Ge or Sn), separated by hydrazinium cations and, for 2, additional neutral hydrazine molecules. Substantial hydrogen bonding exists among the hydrazine/hydrazinium molecules as well as between the hydrazinium cations and the selenide anions. Whereas the previously reported tin(IV) sulfide system, (N(2)H(5))(4)Sn(2)S(6), decomposes cleanly to microcrystalline SnS(2) when heated to 200 degrees C in an inert atmosphere, higher temperatures (>300 degrees C) are required to dissociate selenium from 1 and 2 for the analogous preparations of single-phase metal selenides. The metal chalcogenide salts are highly soluble in hydrazine, as well as in a variety of amines and DMSO, highlighting the potential usefulness of these compounds as precursors for the solution deposition of the corresponding metal chalcogenide films.     

Comprehensive relativistic ab initio and density functional theory studies on PtH, PtF, PtCl, and Pt(NH(3))(2)Cl(2)

Platinum monohydride is taken as an example to compare the performance of various relativistic and correlation approaches, such as all-electron DPT (direct perturbation theory), ECP (effective core potential); RSPT2, RSPT3 (second- and third-order multireference Rayleigh-Schr?dinger perturbation theory), CCSD(T) (coupled-cluster with singles, doubles, and perturbative triples), as well as the four-component relativistic density functional theory. It is shown that first-order DPT performs significantly better than the (first-order) Breit-Pauli Hamiltonian. The performance of different approaches for the excitation energies of the platinum diatomics is discussed critically. The molecular spectroscopic constants for PtF and PtCl are predicted for the first time. The geometric data for several isomers of cis- and trans-Pt(NH(3))(2)Cl(2) are reported. The corresponding energetic data are calculated at relativistic all-electron and ECP-CCSD(T) as well as four-component relativistic density functional levels of theory. Contrary to previous results, it is found that the two C(2v) isomers of cis-Pt(NH(3))(2)Cl(2) are marginally separated in energy, which could be ascribed to Cl-H interactions.     

Acid modified diatomaceous earth--a sorbent material for thin layer chromatography

Natural diatomaceous earth (DE) is modified by flux calcination and refluxing with acid. To characterize natural DE, modified DE's [flux calcinated (FC)DE and FCDE-I] and silica gel 60GF(254) (Si-60GF(254)) are analyzed microscopically, physically, and chemically by various techniques. FCDE-I and Si-60GF(254) are investigated for their usefulness in the stationary phase of thin layer chromatography (TLC) both individually and in composition. Sodium diethyldithiocarbamate (DEDTC) and ammonium pyrrolidinedithiocarbamate (PyDTC) are prepared as Co or Cu (M) complexes [M(DEDTC)(2) and M(PyDTC)(2), respectively]. These complexes and their mixtures are run on thin layers of Si-60GF(254) and FCDE-I individually, and on various FCDE-I and Si-60GF(254) mixtures. Pure toluene and various toluene-cyclohexane mixtures (3:1, 1:1, 1:2, 1:3, v/v) are used as mobile phases for the running the complexes. The best analytical separations of both M(DEDTC)(2) and M(PyDTC)(2) complexes are obtained when using pure toluene and toluene-cyclohexane (3:1, 1:1, v/v) as mobile phases on FCDE-I-Si-60GF(254) (1:3, 1:1, w/w) layers as stationary phases. This study shows that it is possible to qualitatively analyze and to satisfactorily separate a mixture Cu(2+) and Co(2+) cations on cited chromatographic systems.     

The novel sandwich-type heteropolyoxotungstates [M2Bi2(beta-B-MW9O34)2]14- (M = Co(II), Zn(II)): beta-type dimeric heteropolyanions with a transition metal as the central heteroatom and Bi(III) and M as linking atoms

Two new sandwich-type heteropolyoxometalates, Na(14)[Co(2)Bi(2)(beta-B-CoW(9)O(34))(2)].48H(2)O (1) and Na(14)[beta-B-Zn(2)Bi(2)(ZnW(9)O(34))(2)].51H(2)O (2), have been synthesized at pH = 7.5-8 and characterized by elemental analysis, IR, UV-vis, TG-DSC and electrochemistry. Structural analysis indicates that both polyanions, M(2)Bi(2)(beta-B-MW(9)O(34))(2)](14-) (M = Co(II) and Zn(II)), are isomorphic and consist of two unprecedented [beta-B-MW(9)O(34)](12-) subunits linked by two M(II) and two Bi(III) which are coplanar. The polyanions are also the first examples of dimeric heteropolyanions with Bi(III) only as the second (linking) heteroatom and the transition metals (Co(II) or Zn(II)) as the first and second heteroatoms as well. The lower absorption of nu(W-O(d)) (915 cm(-1)) in the IR is a simple and feasible judgment of sandwich-type polyanions with a transition metal ion as a central heteroatom.     

烷基-全氟酰氧基氮氧自由基——全氟酰基过氧化物与脂肪族伯、仲胺单电子转移反应的EPR研究

EPR研究表明,全氟酰基过氧化物在室温下可将脂肪族仲胺氧化成相应的稳定双烷基氮氧自由基。它们与RNH₂的氧化反应是单电子转移过程,生成烷基-全氟酰氧基氮氧自由基RN(O^·)OCOR_F;当R为叔烷基时,还生成RN(O^·)R、RN(O^·)H、RN(O^·)R_F和RN(O^·)R_F′(R_F′=R_F-CF₂)等4种稳定性差别很大的氮氧自由基。EPR研究结果揭示了该反应机理的重要信息。     

Synthesis, X-ray structure, polarized optical spectra and DFT theoretical calculations of two new organic-inorganic hybrid fluoromanganates(III): (bpaH2)[MnF4(H2O)2]2 and (bpeH2)[MnF4(H2O)2]2

Two new fluoromanganates(III) of 1,2-bis(4-pyridyl)ethane (bpa) and trans-1,2-bis(4-pyridyl)ethylene (bpe), LH(2)[MnF(4)(H(2)O)(2)](2) (L = bpa or bpe), have been prepared and their structure have been solved by single-crystal X-ray diffraction. The [MnF(4)(H(2)O)(2)](-) anion displays an octahedral geometry with a strong Jahn-Teller tetragonal distortion along the H(2)O-Mn-OH(2) axis. The equatorial metal-ligand distances (Mn-F 1.827(1)-1.859(2) A) are shorter than the axial ones (Mn-O 2.203(2)-2.234(2) A). Three polarized absorption bands at 22,500, 18,300 and 14,500 cm(-1) are observed in the optical spectra of (bpaH(2))[MnF(4)(H(2)O)(2)](2). Finally, we present theoretical calculations on the equilibrium bond distances as well as the crystal-field electron structure using density functional methods. The calculated Mn-F bond distances (1.85 A) are in agreement with the experimental data but the obtained Mn-O distances (2.53-2.56 A) are higher than the experimental one as usually found in similar Jahn-Teller distorted systems. The calculated d-d transition energies are compared with experimental energies derived from the optical spectra. The variation of the HOMO energy and transition energies against the Mn-O distance is also shown.