双核金属酞菁类化合物催化脱硫机理研究Ⅳ──中心金属离子对MPc－PcM催化活性的影响

Study on the Mechanisms of Catalytic Desulfurization With Binuclear Metallo Phthalocyanine Ⅳ──The Effect of Central Metal Cations for the Catalytic Activity of MPc-PcM

实验研究结果表明双核金属酞菁类化合物ＭＰｃ－ＰｃＭ（Ｍ＝Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ）是催化Ｈ＿２Ｓ液相氧化反应的良好催化剂，且其催化活性顺序为Ｃｏ＞Ｎｉ＞Ｖ＞Ｆｅ＞Ｃｕ＞Ｃｒ＞Ｍｎ．采用量子化学理论计算方法（ＩＮＤＯ／Ｓ）分析了其前线分子轨道的构成特征，结果表明这几种ＭＰｃ－ＰｃＭ的ＬＵＭＯ轨道皆为有金属离子参与形成的π轨道，但ＨＯＭＯ轨道间的差异却很大．Ｍ＝Ｃｏ、Ｎｉ、Ｃｕ、Ｃｒ时，其ＨＯＭＯ为π轨道；而Ｍ＝Ｆｅ、Ｍｎ时，其ＨＯＭＯ却为σ轨道．正是在前线分子轨道的轨道类型、共轭程度及金属轨道贡献三方面因素的协同作用下，才导致ＭＰｃ－ＰｃＭ的催化活性顺序并非按中心金属离子价电子层ｄ电子数的递变而呈现出规律性的变化．

The catalytic activity of binuclear metallo phthalocyanine MPc-PcM (M=V,Cr, Mn, Fe, Co, Ni, Cu) were determined for the oxidation of H_2S in liquid phase. The result revealled that these several kinds of compounds were excellent catalysts for this desulfurization, and their activity order was as follow: Co>Ni>V>Fe>Cu>Cr>Mn. The composition character of their frontier molecular orbitals were analyzed by quantum chemistry methed (INDO/S), the calculated result indicated that the type of the lowest unoccupied molecular orbitals (LUMO) was π orbital for these several compounds, but the highest occupied molecular orbitals (HOMO) were different in forms of π orbital for the case of M=Co, Ni, Cu and Cr, and σ orbital for the case of M= Fe, Mn. It was the coordinated interaction of orbital type, conjugated extent and contribution of metal catio' s orbitals that lead to the activity order of these compounds was not followed with the changed rule of d electron number of central metal cations.