Syntheses and structural characterizations of Fe_4S_4 cubane-like cluster compounds containing cycloalkylthiolate ligands

In a reaction system consisting of FeCl2,tetrathiometallate and cycloalkylthiolate,two Fe4S4 cubane-like cluster compounds were obtained with the following crystallographic data:(PhCH2NMe32[Fe4S4 (SC5H9)4](Ⅰ),monoclinic space group P21/c,a=1.6327(4),6=1.1229(3),c=2.802 5( 10) nm,β=94.63(2)°,Z=4,and R=0.074; (Et4N)2[Fe4S4(SC6H11)4](Ⅱ),tetragonal space group I42m,a=1.16705(9),b=1.167 06(2),c=2.063 26(5) nm,Z=2,Dabs=1.28 g/cm3,and R=0.078 The participation of cy-cloalkylthiolate ligand does not obviously arouse the change of the Fe4S4 core structure.Meanwhile,the influence of the cation on the structural symmetry of the Fe4S4 cluster dianion is also discussed.     

光合反应中心原初电子转移机理的理论研究

用量子化学密度泛函B3LYP方法在3-21G水平上计算细菌光合反应中心原初电子给体P960和绿色植物PSⅡ光合反应中心原初电子给体P680的电子结构,然后研究轴向配位的组氨酸残基和周围蛋白质环境的影响,最后探讨其原初电子转移机理。计算结果表明：(1)细菌光合作用反应中心原初电子给体P960-h的HOMO主要是由与M分支相连的组成单元上原子的原子轨道组成,而它的LUMO则两个组成单元上原子的原子轨道都有贡献;PSⅡ反应中心中原初电子给体P680的HOMO和LUMO均主要由与D1蛋白相连的组成单元上原子的原子轨道组成。这些计算结果能够从反应中心最核心的部分-原初电子给体的电子结构方面解释Rps.uiridis反应中心和PSⅡ反应中心原初电子转移只沿一个分支进行的的途径选择性。(2)虽然与细菌反应中心原初电子给体超分子P960的两个细菌叶绿素分子形成轴向配位的组氨酸残基His并未参与超分子P960-h的HOMO和LUMO的组成,但是由于其轴向配位,使得P960-h的ELUMO显著地升高到高于辅助细菌叶绿素和去镁细菌叶绿素的相应值,使得原初电子转移反应能够顺利进行。否则原初电子转移反应很难进行。PSⅡ反应中心的情况,与细菌反应中心十分相似。(3)细菌反应中心辅助细菌叶绿素(ABChlb)中的Mg离子与最近的组氨酸残基His中的N原子的距离和原初电子给体P960中的相应的Mg-N的距离相似,因此同样应该考虑此轴向配位的组氨酸残基,此时原初电子转移反应是沿L分支从P960-h经ABChlb到去镁细菌叶绿素(BPheob)的两步电子转移过程。而PSⅡ反应中心的辅助叶绿素不存在His的轴向配位,这应是与细菌反应中心的重要区别之一,此时原初电子转移应是沿Dl分支从P680-h到Pheoa的一步电子转移过程,但同时也不能完全排除从P680-h到AChla到Pheoa的二步电子转移过程。     

自然和人工光合作用水裂解催化剂

近年生物光合作用水裂解催化中心的结构研究取得重要进展,为人工模拟光合作用水裂解研究提供了理想的蓝图。人工模拟生物水裂解催化中心、制备高效和廉价的人工水裂解催化剂、获得电能和(或)氢能被认为是解决人类所面临的能源危机和环境污染问题的理想途径。这方面的研究具有重要科学意义和应用价值,同时也是广受关注的重大科学前沿。本文对最近生物水裂解催化中心和其人工模拟研究进展进行了评述。     

固氮酶活性中心FeMo-Cofactor对N2活化方式的探讨

结合实验和理论计算的结果, 讨论了固氮酶的活性中心铁钼辅基(FeMo-co-facto r) 对N₂ 的各种活化方式, 并在此基础上提出了一种新模型, 即N₂ 在FeMo2cofacto r 的内部以“4Fe 端基配位+2Fe 侧基配位”的方式被活化,N₂ 的三重键完全断裂, 断裂产生的两个含N 的碎片分别偏向两侧的“窗口”, 再在H 的进攻下被还原为NH₃, 并分别从两侧的“窗口”离去。     

Syntheses,Crystal Structures and Catalytic Activities of Two Novel Mn_2Dy_2O_2 Complexes

Two novel heteronuclear manganese-dysprosium complexes have been synthesized and characterized, both of which contain a [Mn_2Dy_2O_2] core ligated by eight But CO_2-anions and four neutral ligands. In complex 1, [Mn_2Dy_2O_2(Bu~tCO_2)_8(Bu~tCO_2H)_4], all the four neutral ligands coordinated to Dy~(3+) are pivalic acids; Instead, two of these four pivalic acids have been replaced by ethanol in complex 2 [Mn2 Dy2 O2(Bu~tCO_2)_8(Bu~tCO_2H)_2(CH_3CH_2OH)_2]. The crystal of complex 1(C_(60)H_(112)Dy_2Mn_2O_(26), Mr = 1684.36) belongs to the orthorhombic system, space group Pbca with a =19.853(3), b = 18.565(3), c = 20.952(3) ?, V = 7723(2) ?3, Z = 4, Dc = 1.449 g/cm~3, S = 1.210, μ =2.302 mm~(-1), F(000) = 3448, the final R = 0.0802 and w R = 0.1570 for 8736 independent reflections.The crystal of complex 2(C_(54)H_(104)Dy_2Mn_2O_(24), Mr = 1572.25) belongs to the monoclinic system,space group C2/c with a = 27.814(6), b = 13.194(3), c = 22.912(5) ?, β = 124.89(3)o, V = 6897(3) ?3,Z = 4, Dc = 1.514 g/cm~3, S = 1.086, μ = 2.570 mm~(-1), F(000) = 3208, the final R = 0.0256 and wR =0.0592 for 7763 independent reflections. The cyclic voltammogram and catalytic activity measurements of complex 1 suggest that this type of complex can serve as a catalyst for oxygen-evolving reaction.     

Synthesis and structure of a novel MoFe_4S_4 cubane-like cluster (Me_3PhCH_2N)_2[MoFe_4S_4(SC_6H_(11))_7]

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Synthesis,Structure and Catalytic Activity of a Manganese(Ⅲ) Complex Based on 2-(2-Hydroxyphenyl)-5,6-dichlorobenzimidazole Ligands

A new ligand, 2-(2-hydroxyphenyl)-5,6-dichlorobenzimidazole, H2pbmCl2(1), and a novel MnIII complex, [MnIII(HpbmCl2)(pbmCl2)(DMF)2](2),(DMF = N,N-dimethylformamide), have been synthesized and characterized. The crystal of compound 1(C13H8Cl2N2O, Mr = 279.12) belongs to the monoclinic system, space group P21 with a = 3.770(5), b = 25.20(3), c = 5.865(7) , = 92.727(17)o, V = 556.6(12) 3, Z = 2, Dc = 1.665 g/cm3, S = 1.137, μ= 0.568 mm-1, F(000) = 284, the final R = 0.0876 and wR = 0.2334 for 1848 independent reflections. The molecule is planar due to the presence of a strong intramolecular hydrogen bond between O–H group of phenol and N atom of imidazole. H2pbmCl2(1) molecules are arranged into a one-dimensional linear chain through intermolecular hydrogen bonds(N–H···O and C–H···Cl). The crystal of complex 2(C32H27Cl4MnN6O4, Mr = 756.34) belongs to the monoclinic system, space group P21/c with a = 19.043(10), b = 10.808(5), c = 18.704(11), = 115.540(6)o, V = 3473(3) 3, Z = 4, Dc = 1.446 g/cm3, S = 1.3, μ = 0.733 mm-1, F(000) = 1544, the final R = 0.1219 and wR = 0.2681 for 7811 independent reflections. The Mn ion adopts a distorted octahedral geometry coordinated by two deprotonated H2pbmCl2 ligands and two DMF molecules. The [MnIII(HpbmCl2)(pbmCl2)(DMF)2] molecules are arranged into a three-dimensional structure through hydrogen bonds(N–H···N, C–H···N and C–H···Cl) and weak π···πinteractions. The activity measurements suggest that complex 2 is able to serve as a catalyst for H2O2 disproportionation reaction to form O2 in neutral water solution.     

固氮酶的固氮机理和其人工模拟问题的探讨

固氮酶将N₂ 还原为NH₃ 的过程是自然界实现氮循环的重要环节。本文着重对固氮酶的固氮机理和其活性中心FeMo 辅基的人工模拟合成进行探讨, 其中包括FeMo蛋白中的质子和电子的传递, FeMo 辅基对N₂ 的活化方式,Mo 原子的作用, 固氮活性的测试。最后还就固氮酶的活性中心FeMo 辅基的人工模拟合成进行了探讨。     

含环烷巯基配体的Fe_4S_4类立方烷簇合物的合成和结构表征

报道了 2个含烷巯基配体的Fe4S4类立方烷簇合物 ,它们在氯化亚铁 ,四硫代金属酸盐及环烷硫醇组成的反应体系中生成 ,化合物的结构参数分别为 :[PhCH2 NMe3 ]2 [Fe4S4(SC5 H9) 4](Ⅰ ) ,属单斜晶系 ,空间群P2 1/c,a =1 .6 32 7( 4)nm ,b=1 .1 2 2 9( 3)nm ,c=2 .80 2 5 ( 1 0 )nm ,β =94.6 3( 2 )°,Z =4,R =0 .0 74;(Et4N) 2 [Fe4S4(SC6H11) 4](Ⅱ ) ,,属四方晶系 ,空间群I42m ,a=1 .1 6 70 5 ( 9)nm ,b=1 .1 6 70 6 ( 2 )nm ,c=2 .0 6 32 6 ( 5 )nm ,Z =2 ,Dcalc=1 .2 7g/cm3 ,R =0 .0 78.环烷巯基配体的引入没有引起Fe4S4核心结构的明显变化 ,同时讨论了阳离子对Fe4S4簇阴离子结构对称性的影响     

新奇的Mo/Fe/S原子簇的合成及[Me_3PhCH_2N]_2[MoFe_4S_4(SC_6H_(11))_7]的结构表征

在 (NH4) 2 MoS4,FeCl2 ,NaSC6 H1 1 (C6 H1 1 为环己基 )的甲醇反应体系中得到一种新型的 [Me3PhCH2 N] 2 [MoFe4S4(SC6 H1 1 ) 7]的钼铁硫立方烷原子簇 ,并进行了结构表征 .它的晶体属三斜晶系 ,空间群P 1,a =1.5 2 3 1( 3 )nm ,b =1.610 5 ( 3 )nm ,c=1.83 83 ( 4 )nm ,α =77.18( 3 )° ,β =75 .17( 3 )° ,γ =64 .60 ( 3 )° ,Z =2 .讨论了由于环烷巯基参与而引起的反应产物及其结构变化