EaStCHEM, School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, UK.
Dalton Trans. 2012 Jan 7;41(1):201-7. doi: 10.1039/c1dt11456e. Epub 2011 Oct 21.
We report the preparation and electrochemical studies of a systematic series of mono- and di-nitro-substituted 2,2'-bipyridine (bipy) compounds [x-NO(2)-bipy (x = 3,4) and x,x'-(NO(2))(2)-bipy (x,x' = 3, 4, 5)] and their complexes with platinum(II), [Pt(x-NO(2)-bipy)Cl(2)] and [Pt(x,x'-(NO(2))(2)-bipy)Cl(2)]. The effect of the number and substitution pattern of the nitro groups on the low-lying acceptor molecular orbitals (involved in charge transfer transitions) is probed by in situ UV/Vis/NIR and EPR spectroelectrochemical methods, supported by DFT calculations. The LUMOs of x-NO(2)-bipy (x = 3-5) are largely localised on the NO(2)-pyridyl moiety; this is also true of their {PtCl(2)} complexes but with a small but significant shift of electron density from the nitro groups. The LUMOs of x,x'-(NO(2))(2)-bipy with x = 3 and 5 are delocalised over both NO(2)-pyridyl rings, but for 4,4'-(NO(2))(2)-bipy is localised on a single NO(2)-pyridyl ring. In all cases the LUMO of the [Pt(x,x'-(NO(2))(2)-bipy)Cl(2)] complexes is delocalised over both nitro-pyridyl rings. For all complexes, the 4(4') derivatives allows greatest overlap with metal valence orbitals in the LUMO.
我们报告了一系列单和二硝基取代的 2,2'-联吡啶（bipy）化合物 [x-NO(2)-bipy（x = 3,4）和 x,x'-(NO(2))(2)-bipy（x,x' = 3,4,5）]及其与铂（II）的配合物 [Pt(x-NO(2)-bipy)Cl(2)] 和 [Pt(x,x'-(NO(2))(2)-bipy)Cl(2)]的制备和电化学研究。通过原位 UV/Vis/NIR 和 EPR 光谱电化学方法，结合 DFT 计算，研究了硝基数量和取代模式对低能受主分子轨道（涉及电荷转移跃迁）的影响。x-NO(2)-bipy（x = 3-5）的 LUMO 主要定域在 NO(2)-吡啶基部分；这对于它们的 {PtCl(2)} 配合物也是如此，但电子密度从硝基部分有一个小但显著的转移。x,x'-(NO(2))(2)-bipy（x = 3 和 5）的 LUMO 分布在两个 NO(2)-吡啶环上，但 4,4'-(NO(2))(2)-bipy 定域在单个 NO(2)-吡啶环上。在所有情况下，[Pt(x,x'-(NO(2))(2)-bipy)Cl(2)] 配合物的 LUMO 都分布在两个硝基吡啶环上。对于所有配合物，4(4') 衍生物允许与 LUMO 中的金属价轨道最大重叠。
