Synthesis and Characterization of [Fe3(As3)3(As4)]3−, a Binary Fe/As Zintl Cluster With an Fe3 Core

We report here the synthesis and structural characterization of the first binary iron arsenide cluster anion, [Fe₃(As₃)₃(As₄)]³⁻, present in both [K([2.2.2]crypt)]₃[Fe₃(As₃)₃(As₄)] ( 1 ) and [K(18-crown-6)]₃[Fe₃(As₃)₃(As₄)]⋅en ( 2 ). The cluster contains an Fe₃ triangle with three short Fe−Fe bond lengths (2.494(1) Å, 2.459(1) Å and 2.668(2) Å for 1 , 2.471(1) Å, 2.473(1) Å and 2.660(1) Å for 2 ), bridged by a 2-butene-like As₄ unit. An analysis of the electronic structure using DFT reveals a triplet ground state with direct Fe−Fe bonds stabilizing the Fe₃ core.     

Crystal Structure,Spectroscopic Characterization,and Electrochemical and Thermal Stability Properties of a Dinuclear Nickel(Ⅱ) Complex

A new nickel(Ⅱ) complex Ni_2(L)_2(2,2?-bipy)2·5.5H_2 O with methy-bicycle[2.2.1]hept-5-ene-2,3-dicarboxylic acid(H2L) and 2,2?-bipyridine(2,2?-bipy) as ligands has been synthesized in the mixed solvent DMF and water(v:v = 5:2). It crystallizes in the triclinic space group P1 with a = 10.414(2), b = 12.884(3), c = 16.176(4) ?, α = 70.715(5), β = 80.599(5), γ = 77.383(6)o, V = 1989.4(8) ?3, Dc = 1.531 g/cm3, Z = 2, F(000) = 958, GOOF = 1.028, the final R = 0.0808 and w R = 0.2036. The crystal structure shows that the whole molecule consists of two independent dinuclear units, in which two nickel ions are bridged by two μ2-η1:η0 3-carboxylate groups of L2- anions. The coordination environment of Ni(Ⅱ) ion is Ni N_2O_3, giving a distorted square pyramidal geometry. The thermal stability and electrochemical properties of the complex were investigated.     

From an {Fe4S4}-cluster to {Fe2S2}- and {Fe3S}-carbonyls. Crystal structure of [Fe3S(CO)9]2−

We report the electrochemical and chemical synthesis of the first isolable iron carbonyls obtained directly from an {Fe₄S₄}-cluster and carbon monoxide: the structure of one product of chemical reduction, [Fe₃S(CO)₉]²⁻, had been determined by X-ray crystallography.     

Study on the Synthesis and Characterization of Novel Immobilized β-Cyclodextrin Polymer (Ⅰ)

A series of novel β-cyclodextrin polymers was synthesized by immobilization of β-cyclodextrin on the chloromethylated crosslinked polystyrene carriers. The synthetic conditions such as reaction time, temperature, molar feeding ratio of reactants, the degree of crosslinking of polystyrene and the catalysts used were studied in detail and the chemical and physical structures of the formed β-CDpolymers were characterized. Results show that the preparation method is simple and the amount of β-CD immobilized is high. As biomedical adsorbents, they were tested for removal of various endogenous and exogenous toxins such as phenols, aromatic amins, barbitals and unconjugated bilirubin. Results indicate that the adsorptión capacity for those toxins can be enhanced by the inclusion interaction among the β-CD, the substrate molecules and the β-CD polymers.     

Synthesis,Crystal Structure,Spectroscopic Characterization,Thermal Stability and Magnetic Properties of a Dinuclear Copper(Ⅱ) Complex

A new copper(Ⅱ) complex [Cu2(MNA)2(2,2‘-bipy)2]·2.5H2 O with methy-5-norbornene-2,3-dicarboxylic acid(MNA) and 2,2’-bipyridine as ligands has been synthesized in the mixed solvents of DMF and water.It crystallizes in monoclinic,space group P 1,with a = 10.4191(11),b = 12.8883(13),c = 16.1114(16) ?,α = 70.8090(10),β = 80.568(2),γ = 77.440(2)o,V = 1984.3(4) ?3,Dc = 1.551 g/cm3,Z = 2,F(000) = 962,the final GOOF = 1.051,R = 0.0431 and w R= 0.0980.The crystal structure shows that the whole molecule consists of two independent dinuclear units,in which two copper ions are bridged by two μ2-η1:η0 3-carboxylate groups of MNA2-.The coordination environment of Cu(Ⅱ) ion is Cu O3N2,giving a distorted square pyramidal geometry.The spectroscopic characterization,thermal stability and magnetic properties of the complex were investigated.     

Photoconduction in [Fe(Htrz)2(trz)](BF4)·H2O nanocrystals

Sub-micron-sized [Fe(Htrz)(2)(trz)](BF(4))·H(2)O nanoparticles that exhibit a spin crossover transition are positioned between Au electrodes with sub-100 nm separation. After voltage poling, samples exhibit unexpected large conductivity, with photoconductance and photovoltaic behavior.     

Synthesis,Characterization and Catalytic Activity of Polyoxometalates Derived from α-P_2W_(15)O_56~(12

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Synthesis, Structure Characterization and Biological Activity of a Novel Polyoxovanadate Cluster: [NH3(CH2)2NH2(CH2)2NH3]4·[VⅤ6VⅣ12O42(PO4)](PO4)·2H2O

A new polyoxovanadate cluster,[NH3(CH2)2NH2(CH2)2NH3]4[VⅤ6VⅣ12O42(PO4)](PO4)·2H2O, has been synthesized and characterized by means of elemental analysis, IR spectrometry, EPR spectrometry, TG analysis and single crystal X-ray diffraction. This compound crystallizes in a monoclinic space group C2/c with a=2.3912(5) nm, b=1.3002(3) nm, c=2.0172(4) nm, β=105.75(3)°, V=6.036(2) nm3, Z=2, R1=0.0572, wR2=0.1476. It has a superKeggin structure with a Keggin unit capped by six [VO5] moieties on the pits on every side of the Keggin unit. The anti-tumor activity of the compound was estimated in three human tumor cell lines in vitro.     

Synthesis,Characterization and Crystal Structure of (PhCH2)2Sn(S2CENt2) and (PhCH2)2Sn(S2CNC4H8)2

Two new dibenzyltin bisditiocarbamates(PhCH2)2 Sn(S2CNEt2)2(1) and (PhCH2)2 Sn(S2CNC4H8)2(2) were synthesized by the reaction of dibenzyltin dichloride with dithiocarbamates and characterized by elemental analysis ,IR,^1H NMR and MS spectra.The crystal structures were determined by X-ray single crystal diffraction analysis.In both complexes,the tin atom is six-coordinated in a distorted octahedral configuration.In the crystals of 1,the molecular packing in unit cell reveals that the two adjacent molecules are symmetrically linked to each other in dimers by two Sn S interactions of 0.3816nm.In the crystals of 2,the molecules are packed in the unit cell in one-dimensional chain structure linked by weaker intermolecular S S conmtacts.     

Synthesis and Structural Characterization of a Cyano-bridged 1-D Lanthanum(Ⅲ)-iron(Ⅲ)Complex [La(DMSO)5(H2O)](μ-CN)2[Fe(CN)4]·H2O

A new lanthanumⅢ-ironⅢ complex [La(DMSO)5(H2O)](μ-CN)2[Fe(CN)4]·H2O 1 (DMSO=dimethylsulfoxide) has been prepared by a facile approach, ball-milling method, and characterized by X-ray diffraction. The crystal belongs to monoclinic, space group P21/n with a=9.7125(3), b=21.5336(7), c=14.3804(5) (A), β=93.242(3)°, C16H34FeLaN6O7S5, Mr=777.55, V=3002.8(2)(A)3, Z=4, Dc=1.720 g/cm3, S=1.053, μ(MoKα)=2.278 mm-1, F(000)=1564, R=0.0490 and wR=0.1270. The crystal structure analysis of 1 reveals a slightly distorted squareantiprism eightfold-coordinated La(Ⅲ) ion and a 1-D zigzag chain structure extending through the Fe-CN-La-NC-Fe linkages. The [La(DMSO)5(H2O)](μ-CN)2[Fe(CN)4] species are held together via hydrogen bonds to form a three-dimensional framework.     

Syntheses, structure, and a Mössbauer and magnetic study of Ba(4)Fe(2)I(5)S(4)

The compound Ba4Fe2I5S4 has been prepared at 1223-1123 K by the "U-assisted" reaction of FeS, BaS, S, and U with BaI2 as a flux. A more rational synthesis was also found; however, the presence of U appears to be essential for the formation of single crystals suitable for X-ray diffraction studies. Ba4Fe2I5S4 crystallizes in a new structure type with two formula units in space group I4/m of the tetragonal system. The structure consists of a Ba-I network penetrated by (1)infinity[Fe2S4] chains. Each Fe atom, which is located on a site with 4 symmetry, is tetrahedrally coordinated to four S atoms. The FeS4 tetrahedra edge-share to form linear (1)infinity[Fe2S4] chains in the [001] direction. The Fe-Fe interatomic distance in these chains is 2.5630(4) A, only about 3% longer than the shortest Fe-Fe distance in -Fe metal. Charge balance dictates that the average formal oxidation state of Fe in these chains is +2.5. The M?ssbauer spectra obtained at 85 and 270 K comprise a single quadrupole doublet that has hyperfine parameters consistent with an average Fe oxidation state of +2.5. The M?ssbauer spectrum obtained at 4.2 K consists of a single magnetic sextet with a small hyperfine field of -15.5 T. This spectrum is also consistent with rapid electron delocalization and an average Fe oxidation state of +2.5. The molar magnetic susceptibility of Ba4Fe2I5S4, obtained between 3.4 and 300 K, qualitatively indicates the presence of weak pseudo-one-dimensional ferromagnetic exchange within a linear chain above 100 K and weak three-dimensional ordering between the chains at lower temperatures.     

Preparation and Characterization of the Solid Inclusion Compounds of α-, β-Cyclodextrin with Phenylalanine (D-, L- and DL-Phe) and Tryptophan (D-, L- and DL-Trp)

The solid cyclodextrin (α-, β-CD) inclusion compounds of phenylalanine (D-, L- and DL-Phe) and tryptophan (D-, L-?and DL-Trp) were prepared and the stoichiometry of host and guest in the supermolecules was determined to be 1:1 based on elemental analyses. β-CD formed inclusion compounds with α-aromatic amino acid (α-AAA) in higher yield in contradistinction to α-CD. The yields of the α- or β-CD inclusion compounds of a pair of optical isomers of chiral aromatic amino acids and their racemic modification decreased in the order L->DL->D-form. The complexation between CD and α-AAA caused a change in shape, location and diffracted intensity of the X-ray diffraction peaks of both host and guest. The decomposition temperature of the inclusion compounds was not only slightly higher than that of a pure host but also remarkably higher than that of a pure guest. Upon inclusion the signals of CD protons inside the cavity shifted to upfield while those of the protons outside the cavity had only smaller changes, and the proton signals of the aromatic ring of guest shifted to a certain extent. The chemical shift changes of 4-H and 5-H located in small end side of cavity were a bit bigger than those of 2-H and 3-H located in large one, suggesting that aromatic ring of a guest molecule within a host cavity might be kept near small end side of?cavity. An ESI-MS experiment has proved the formation and stability of the 1:1 CD inclusion compounds of α-AAA in aqueous solution.     

Evidence from Mössbauer spectroscopy for distinct [2Fe-2S](2+) and [4Fe-4S](2+) cluster binding sites in biotin synthase from Escherichia coli

Biotin synthase is an AdoMet-dependent radical enzyme that catalyzes the insertion of an FeS cluster-derived sulfur atom into dethiobiotin. The dimeric enzyme is purified containing one [2Fe-2S]2+ cluster per monomer, but it is most active when reconstituted with an additional [4Fe-4S]2+ cluster per monomer. Using M?ssbauer spectroscopy coupled with differential reconstitution of each cluster with 57Fe, we show that the reconstituted enzyme has approximately 1:1 [2Fe-2S]2+ and [4Fe-4S]2+ clusters and that the [4Fe-4S]2+ cluster is assembled at an alternate site not previously occupied by the [2Fe-2S]2+ cluster. These data suggest that biotin synthase is evolved to simultaneously accommodate two different clusters with unique roles in catalysis.     

Synthesis and crystal structure of Nb2S4(S2NCEt2)4, the first molecular complex containing an [Nb2(μ2-S2)2]4+ fragment

The crystal structure was determined for Nb₂S₄(S₂NCEt₂)₄ obtained in 48% yield by the reaction of Cs₄Nb₂S₄(NCS)₈ with NaS₂CNEt₂ in water: a=21.181(8), b=6.958(1), c=16.623(6) Å, =133.95(2)^o, V = 1764(1) ų, space group C2/m, Z=2, d_calc=1.708 g/cm³. The measurements were carried out on a Syntex P2₁ diffractometer with CuK radiation. A total of 2536 reflections were measured, of which 990 were used, R_aniso=0.0444. The basic fragment in this molecule is [Nb₂(₂–S₂)₂]⁴⁺, the Nb–Nb distance in which corresponds to a metal-metal single bond. The molecule is partially disordered over two positions about the twofold axis and mirror plane of the C2/m space group. The dithiocarbamate and disulfide ligands with bidentate coordination form a distorted square antiprism about each of the niobium atoms as in NbS₂Cl₂. The anomalously large S–S bond length in the S₂ ligand [2.282(5) Å] may be attributed to inaccuracy in the determination due to disorder.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 134–138, March–April, 1993.     

Isolation and Spectroscopic Characterization of Protonated Mixed [Tetrakis (4-pyridyl)porphyrinato] (phthalocyaninato)Rare Earth (Ⅲ)Double-decker Compounds

IntroductionThe homoleptic sandwich~type porphyrinato and phthalocyaninato metal complexesRE (P) z and RE2 (P) 3 (RE =rare earth 1 P = Por or Pc) have been intensively studied over sev-eral decades due to their potential application in non-linear optical (NLO) materials, molecu-lar electronic and magnetic ..te.i.l.L1--l6j.The double-deckers have also aroused a growing interest as structural and spectroscopicsynthetic models for the dimmer of bacteriochlorophyl1 molecules in bacterial pho…