Department of Chemistry and MacDiarmid Institute for, Advanced Materials and Nanotechnology, University of Otago, P.O. Box 56, Dunedin, 9054, New Zealand.
Département de Chimie, Université de Montréal, 2900 Boulevard Edouard-Montpetit, Montréal, Quebec, H3T 1J4, Canada.
Chemistry. 2018 Jul 11;24(39):9820-9832. doi: 10.1002/chem.201800396. Epub 2018 Jun 13.
Seventeen cobalt complexes-eleven dinuclear cobalt(II) complexes and three tetranuclear cobalt complexes (two mixed valent) of ditopic ligands, with varying N-donor aromatic bridging moieties and pendant pyridine side arms, as well as three mononuclear cobalt(II) complexes of Schiff base macrocyclic ligands-have been screened for photocatalytic hydrogen evolution reaction (HER) activity. All 17 complexes are active catalysts for the HER, in both DMF and aqueous solution, in tandem with the [Ru(bpy) ] (bpy=2,2'-bipyridine) photosensitiser. All are benchmarked to the literature standard [Co (dmgH) (py)Cl] (dmg=dimethylglyoxime, py=pyridine) under identical conditions. Two families of dinuclear cobalt(II) complexes of bis-tetradentate ligands that provide a triazole bridging moiety and mononuclear cobalt(II) complexes of tetradentate Schiff base macrocycles were found to be the most active catalysts, outperforming [Co (dmgH) (py)Cl] by two- to three-fold. Within these two families, the use of shorter alkyl linkers between the N donors, and hence, smaller chelate ring sizes, was found to significantly enhance catalytic performance, whereas the variation of peripheral functional groups was found to have little effect. This last point will be convenient for subsequent surface immobilisation studies.
十七种钴配合物-十一种双核钴(II)配合物和三种四核钴配合物（两种混合价态），配体为双齿配体，具有不同的 N-供体芳族桥接部分和吡啶侧臂，以及三种席夫碱大环配体的单核钴(II)配合物-已被筛选用于光催化析氢反应 (HER) 活性。所有 17 种配合物都是 HER 的活性催化剂，在 DMF 和水溶液中均与 [Ru(bpy)]（bpy=2,2'-联吡啶）光敏剂串联使用。所有配合物均在相同条件下与文献标准 [Co(dmgH)(py)Cl]（dmg=二甲基乙二肟，py=吡啶）进行基准测试。发现两种双四核钴(II)配合物的二齿配体家族，提供三唑桥接部分和单核钴(II)的四齿席夫碱大环配合物是最活跃的催化剂，比 [Co(dmgH)(py)Cl] 高出两到三倍。在这两个家族中，发现 N 供体之间使用较短的烷基连接体，从而减小螯合环的尺寸，可显著提高催化性能，而外围官能团的变化则发现几乎没有影响。这最后一点将方便后续的表面固定化研究。
