Arachchige Shamindri M, Brown Jared R, Chang Eric, Jain Avijita, Zigler David F, Rangan Krishnan, Brewer Karen J
Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0212, USA.
Inorg Chem. 2009 Mar 2;48(5):1989-2000. doi: 10.1021/ic8017387.
Supramolecular complexes coupling Ru(II) or Os(II) polyazine light absorbers through bridging ligands to Rh(III) or Ir(III) allow the study of factors impacting photoinitiated electron collection and multielectron water reduction to produce hydrogen. The {(bpy)(2)Ru(dpb)}(2)IrCl(2)(5) system represents the first photoinitiated electron collector in a molecular system (bpy = 2,2'-bipyridine, dpb = 2,3-bis(2-pyridyl)benzoquinoxaline). The {(bpy)(2)Ru(dpp)}(2)RhCl(2)(5) system represents the first photoinitiated electron collector that affords photochemical hydrogen production from water in the presence of an electron donor, N,N-dimethylaniline (dpp = 2,3-bis(2-pyridyl)pyrazine). The complexes {(bpy)(2)Ru(dpp)}(2)RhCl(2)(5), {(bpy)(2)Ru(dpp)}(2)RhBr(2)(5), {(phen)(2)Ru(dpp)}(2)RhCl(2)(5), {(bpy)(2)Os(dpp)}(2)RhCl(2)(5), {(tpy)RuCl(dpp)}(2)RhCl(2)(3), {(tpy)OsCl(dpp)}(2)RhCl(2)(3), and {(bpy)(2)Ru(dpb)}(2)IrCl(2)(5) are herein evaluated with respect to their functioning as hydrogen photocatalysts (tpy = 2,2':6',2''-terpyridine, phen = 1,10-phenanthroline). With the exceptions of {(bpy)(2)Ru(dpb)}(2)IrCl(2)(5) and {(tpy)OsCl(dpp)}(2)RhCl(2)(3), all other complexes demonstrate photocatalytic activity. The functioning systems possess a rhodium localized lowest unoccupied molecular orbital that serves as the site of electron collection and a metal-to-ligand charge-transfer ((3)MLCT) and/or metal-to-metal charge-transfer ((3)MMCT) excited-state with sufficient driving force for excited-state reduction by the electron donor. The lack of photocatalytic activity by {(bpy)(2)Ru(dpb)}(2)IrCl(2)(5), although photoinitiated electron collection occurs, establishes the significance of the rhodium center in the photocatalytic system. The lack of photocatalytic activity of {(tpy)OsCl(dpp)}(2)RhCl(2)(3) is attributed to the lower-energy (3)MLCT state that does not possess sufficient driving force for excited-state reduction by the electron donor. The variation of electron donor showed the photocatalysis efficiency to decrease in the order N,N-dimethylaniline > triethylamine > triethanolamine. The general design considerations for development of supramolecular assemblies that function as water reduction photocatalysts are discussed.
通过桥连配体将钌（II）或锇（II）多嗪光吸收剂与铑（III）或铱（III）偶联而成的超分子配合物，有助于研究影响光引发电子收集以及多电子水还原制氢的因素。{(bpy)(2)Ru(dpb)}(2)IrCl(2)(5)体系是分子体系中的首个光引发电子收集器（bpy = 2,2'-联吡啶，dpb = 2,3-双（2-吡啶基）苯并喹喔啉）。{(bpy)(2)Ru(dpp)}(2)RhCl(2)(5)体系是首个在电子供体N,N-二甲基苯胺存在下能从水中实现光化学产氢的光引发电子收集器（dpp = 2,3-双（2-吡啶基）吡嗪）。本文对配合物{(bpy)(2)Ru(dpp)}(2)RhCl(2)(5)、{(bpy)(2)Ru(dpp)}(2)RhBr(2)(5)、{(phen)(2)Ru(dpp)}(2)RhCl(2)(5)、{(bpy)(2)Os(dpp)}(2)RhCl(2)(5)、{(tpy)RuCl(dpp)}(2)RhCl(?)(3)、{(tpy)OsCl(dpp)}(2)RhCl(2)(3)以及{(bpy)(2)Ru(dpb)}(2)IrCl(2)(5)作为氢光催化剂的功能进行了评估（tpy = 2,2':6',2''-三联吡啶，phen = 1,10-菲咯啉）。除{(bpy)(2)Ru(dpb)}(2)IrCl(2)(5)和{(tpy)OsCl(dpp)}(2)RhCl(2)(3)外，所有其他配合物均表现出光催化活性。起作用的体系具有一个铑局域化的最低未占据分子轨道，作为电子收集位点，以及一个具有足够驱动力供电子供体进行激发态还原的金属-配体电荷转移（(3)MLCT）和/或金属-金属电荷转移（(3)MMCT）激发态。{(bpy)(2)Ru(dpb)}(2)IrCl(2)(5)虽然发生了光引发电子收集，但缺乏光催化活性，这确立了铑中心在光催化体系中的重要性。{(tpy)OsCl(dpp)}(2)RhCl(2)(3)缺乏光催化活性归因于其较低能量的(3)MLCT态，该态不具有足够的驱动力供电子供体进行激发态还原。电子供体的变化表明光催化效率按N,N-二甲基苯胺>三乙胺>三乙醇胺 的顺序降低。讨论了作为水还原光催化剂的超分子组装体开发的一般设计考量。
