School of Chemical Sciences, Dublin City University, Dublin 9, Ireland.
Dalton Trans. 2014 Mar 7;43(9):3576-83. doi: 10.1039/c3dt53166j.
Two porphyrin-cobaloxime complexes; [{Co(dmgH)2Cl}{MPyTPP}] () and [{Co(dmgH)2Cl}{ZnMPyTPP}] () (dmgH = dimethylglyoxime, MPyTPP = 5-(4-pyridyl)-10,15,20-triphenylporphyrin) have been synthesised as model systems for the generation of hydrogen from water. Although initially envisaged as photocatalytic systems neither complex catalysed the reduction of water to hydrogen following irradiation. However, both complexes are molecular precursors for hydrogen evolution under electrochemical conditions. Turnover numbers for hydrogen production of 1.8 × 10(3) and 5.1 × 10(3) were obtained for and respectively following potentiostatic electrolysis at -1.2 V vs. Ag/AgCl while cobaloxime alone produced a turnover-number of 8.0 × 10(3). The photophysical properties of and were examined to provide an explanation for the lack of photochemical activity. These results, coupled with quantum chemical calculations, confirm that porphyrins fail to act as light-harvesting units for these systems and that the lowest energy excited states are in fact cobaloxime-based rather than porphyrin based.
两种卟啉-钴配合物；[{Co（dmgH）2Cl}{MPyTPP}]（）和[{Co（dmgH）2Cl}{ZnMPyTPP}]（）（dmgH=二甲基乙二肟，MPyTPP=5-（4-吡啶基）-10,15,20-三苯基卟啉）已被合成作为从水中产生氢气的模型系统。虽然最初设想为光催化系统，但这两种配合物在光照下都没有催化水还原为氢气。然而，在电化学条件下，这两种配合物都是氢析出的分子前体。在-1.2 V 对 Ag/AgCl 进行恒电位电解时，分别获得了和的产氢周转数为 1.8×10(3)和 5.1×10(3)，而单独的钴配合物的产氢周转数为 8.0×10(3)。和的光物理性质进行了研究，以解释其缺乏光化学活性的原因。这些结果与量子化学计算相结合，证实卟啉不能作为这些体系的光收集单元，并且最低能量激发态实际上是基于钴配合物而不是基于卟啉。
