Photoinduced four- and six-electron reduction of mononuclear ruthenium complexes having NAD+ analogous ligands
作者:Takashi Fukushima、Tohru Wada、Hideki Ohtsu、Koji Tanaka
DOI:10.1039/c0dt00504e
日期:——
The ruthenium complexes [Ru(bpy)(pbn)2](PF6)2 ([2]2+; bpy = 2,2′-bipyridine, pbn = 2-(2-pyridyl)benzo[b]-1,5-naphthyridine) and [Ru(pbn)3](PF6)2 ([3]2+) were synthesized. Photoirradiation (λ > 420 nm) of [2]2+ and [3]2+ in CH3CN/triethanolamine (TEOA) brought about proton coupled four- and six-electron reduction of the complexes to produce [Ru(bpy)(pbnH2)2](PF6)2 ([2·H4]2+; pbnH2 = 5,10-dihydro-2-(2-pyridyl)benzo[b]-1,5-naphthyridine) and [Ru(pbnH2)3](PF6)2 ([3·H6]2+), respectively. The photoexcited [RuIII(bpy)(pbn˙−)(pbnH2)]2+ intermediate is quenched by intermolecular electron transfer from TEOA to RuIII, while intramolecular transfer from pbnH2 to RuIII is negligible. As a result, novel photochemical four- and six-electron reduction of [2]2+ and [3]2+ is achieved through repetition of the two-electron reduction of the Ru-pbn group. The high efficiency photochemical two-, four- and six-electron reductions of [Ru(bpy)2(pbn)]2+ ([1]2+), [2]2+ and [3]2+, respectively, by taking advantage of proton coupled two electron reduction of NAD+ analogous type ligands such as pbn opens a general pathway for multi-electron reduction of metal complexes via illumination with visible light.
钌配合物[Ru(bpy)(pbn)2](PF6)2 ([2]2+; bpy = 2,2′-联吡啶, pbn = 2-(2-吡啶基)苯并[b]-1,5-萘啶)和[Ru(pbn)3](PF6)2 ([3]2+)被合成。在CH3CN/三乙醇胺(TEOA)中对[2]2+和[3]2+进行光照射(λ > 420 nm),实现了配合物的质子耦合四电子和六电子还原,分别生成[Ru(bpy)(pbnH2)2](PF6)2 ([2·H4]2+; pbnH2 = 5,10-二氢-2-(2-吡啶基)苯并[b]-1,5-萘啶)和[Ru(pbnH2)3](PF6)2 ([3·H6]2+)。光激发的[RuIII(bpy)(pbn˙−)(pbnH2)]2+中间体通过分子间电子从TEOA转移到RuIII而被淬灭,而分子内从pbnH2到RuIII的转移可以忽略不计。因此,通过重复Ru-pbn基团的二电子还原,实现了新型光化学四电子和六电子还原反应。利用质子耦合二电子还原类似NAD+的配体如pbn,通过可见光照射,实现了[Ru(bpy)2(pbn)]2+ ([1]2+), [2]2+和[3]2+的高效光化学二电子、四电子和六电子还原,为金属配合物的多电子还原打开了一条通用途径。