二高氯酸根.(二亚乙基三胺).咪唑合铜(Ⅱ)的合成与结构

已知多种金属酶和金属蛋白中的金属离子与肽链上的组氨酸残基的咪唑基配位构成其活性中心的重要部分。在Cu、Zn超氧化物歧化酶和细胞色素C氧化酶a_3中、组氨酸的咪唑基成为连接Cu、Zn或Cu、Fe原子的桥基尤为突出。作为超氧化物歧化酶活性中心结构与性能关联研究的一部分,我们首先合成一初级物[Cu(ImH)(dien)(ClO_4)_2并用X光单晶衍射测定了它的结构。按衍射系统消光,晶体属于正交晶系空间群Pna2_1或Pnma。由于分子中重原子的特殊分布和咪唑环的无序取向,按这两个空间群均可得到晶体结构相近的解析结果,从而面临在有心和无心空间群对之间作出选择这一棘手问题。本文主要报导按Pnma求解结构和分子结构的特征。

SYNTHESIS AND STRUCTURE OF DI-PERCHLORATODI-ETHYLENE-TRI-AMINE-IMIDAZOLE-COPPER (Ⅱ) [Cu(ImH) (dien) (CLO4)2]

As part of our study of the structure-properties of the active centre in the superoxide dismutase, the title compound was synthesized and its single crystal structure was determined by X-ray diffraction method. The title compound is orthorhombic, Pnma, a=1.4061(1), b=1.2347(2), c=0.9308(1) nm, V=1.6160 nmZ=4, D_c=1.782g cm~(-3) D_0=1.78g cm~(-3) μ(MoK_α)=17.3cm~(-1) F(000)=884. Structure was determined by direct method using MULTAN-82 and refined by fullmatrix least-squares to a R value of 0.055 using 1344 reflections. The molecule is mirror symmetric with the imidazole ring disordered and the Cu atom located in a tetragonally distorted octahedral enviroment of the coordination type 4+2 with four nitrogen atoms from diethylenetriamine and imidazole in square planar configuration and two oxyzen atoms from perchlorate ions in the axial positions. The reason we prefer to describe the structure in centrosymmetric space group is briefly discussed.