光系统II中新型高价模型化合物合成及性能测试

Synthesis and characterization of a novel high valent dinuclear Mn^(III,III) complex of triphenolate ligand [N_4O_3]^(3-) as a model for OEC in PSII

设计、合成了一个新的光合作用给体部分的模型化合物:[Mn2(III,III)L(μ-OAc)2].PF6(化合物1),其中L为2,6-二{[(2-羟基-5-叔丁基苄基)(吡啶-2-亚甲基)-氨基]-亚甲基}-4-甲基苯酚.与以往的模型体系[Mn2(II,II)(bpmp)(μ-OAc)2].ClO4(化合物8)相比,新模型增加了2个酚配体及2个叔丁基.此化合物中2个以伪八面体形状配位的Mn离子通过1个酚基和2个二齿羧基相连.这些基团的引入提高了中心金属Mn的价态,并增加了配体的电子云密度,从而降低了Mn的氧化还原电位.该模型进一步缩小了人工模型体系与天然光合作用释氧中心(OEC)四核锰簇的差异.通过IR、ESI-MS、NMR(gCOSY、gHMBC、gHSQC)及电化学对新配体及络合物进行了表征和测试.

A new high valent [Mn_2(III/III)L(μ-OAc)_2]·PF_6 complex is prepared, where L is 2,6-bis (((2-hydroxy-5-tert-butylbenzyl)(pyridyl-2-methylene)amino)methylene)-4-methylphenol, which contains additional phenolate functional groups and tert-butyl groups compared to [Mn_2(II/II)(bpmp)(μ-OAc)_2]·ClO_4. In this complex, two pseudo-octahedrally coordinated Mn ions are bridged by a phenolate group and two bidentate acetate ligands. The stronger and more coordinate bonds between anionic phenolate groups and Mn ions in higher oxidation state prevent the dissociation of central ions. The additional tert-butyl groups improve the solubility and electronic cloud density of the ligand. These improvements narrow the disparity between the new model and (Mn)_4 cluster (oxygen-evolving center in nature). IR, ESI-MS, NMR (gCOSY, gHMBC, gHSQC) and electrochemistry characterized the new ligand or complex.