功能性咪唑基钒氧配合物的合成、结构与仿生催化

在室温条件下,甲醇体系中设计合成了一种新的以咪唑为配体的功能性钒氧配合物VO(imidazole)4(SO4).H2O(1)。进行了元素分析、红外光谱表征,并用X-ray单晶衍射法测定了配合物1的晶体结构。配合物1的晶体属于正交晶系,空间群:Pna21,a=1.3844(3)nm,b=0.9786(2)nm,c=1.3617(3)nm,α=β=γ=90°,V=1.8447(6)nm3,Z=4。对配合物1的溴化催化活性进行了研究,通过实验得到了对苯酚红催化溴化的反应速率常数k=2.7600×107L2/(mol2.s)。讨论了配合物1的热稳定性,并结合从头计算结果进一步分析了配合物的稳定性及分子中配键的共价特征。分析结果表明,V—O1的键序(1.0553)明显要比V—O2(0.3942)的键序大,V—N键序接近(0.3336～0.3419),配合物1的中心钒原子周围的价键类型均属于共价键范畴,键序分析结果与晶体结构测定的键长结果一致。

Synthesis, Crystal Structure and Mimic Catalytic Activity of Functional Oxovanadium Complex with Imidazole

A new functional monomeric complex of oxovanadium(Ⅳ), VO(imidazole)₄(SO₄)·H₂O(1) was synthesized from the reaction of VOSO₄·nH₂O with imidazole in methanol at room temperature. The complex was characterized by elemental analysis, IR spectrometry and single crystal X-ray diffraction. Structure analysis reveals that complex 1 crystallized in an orthorclinic system with space group Pna21, a=1.384 4(3) nm,b=0.978 6(2) nm,c=1.361 7(3) nm,α=β=γ=90°,V=1.844 7(6) nm3,Z=4. Bromination reaction activity of the complex was evaluated by the method with phenol red as organic substrate in the presence of H₂O₂, Br- and phosphate buffer. The reaction rate constant(k) for complex 1 was calculated as 2.760 0×10⁷ L²/(mol²·s). The electronic structure and the bonding characters of the complex were analyzed with ab initio calculation. The atomic net charge distribution in the molecular system indicates obvious covalent interaction between the coordinating atoms and vanadium, the bond order of V—O1(1.0553) is obviously larger than that of V—O2(0.3942), the bond order of the four V—N bonds(0.3336～0.3419) is similar. The results are consistent with the structure analysis of the complex.