On the electronic structure of nitro-substituted bipyridines and their platinum complexes
作者:Paul R. Murray、Stephen Crawford、Alice Dawson、Alexander Delf、Calum Findlay、Lorna Jack、Eric J. L. McInnes、Salma Al-Musharafi、Gary S. Nichol、Iain Oswald、Lesley J. Yellowlees
DOI:10.1039/c1dt11456e
日期:——
We report the preparation and electrochemical studies of a systematic series of mono- and di-nitro-substituted 2,2′-bipyridine (bipy) compounds [x-NO2-bipy (x = 3,4) and x,x′-(NO2)2-bipy (x,x′ = 3, 4, 5)] and their complexes with platinum(II), [Pt(x-NO2-bipy)Cl2] and [Pt(x,x′-(NO2)2-bipy)Cl2]. 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 situUV/Vis/NIR and EPR spectroelectrochemical methods, supported by DFT calculations. The LUMOs of x-NO2-bipy (x = 3–5) are largely localised on the NO2-pyridyl moiety; this is also true of their PtCl2} complexes but with a small but significant shift of electron density from the nitro groups. The LUMOs of x,x′-(NO2)2-bipy with x = 3 and 5 are delocalised over both NO2-pyridyl rings, but for 4,4′-(NO2)2-bipy is localised on a single NO2-pyridyl ring. In all cases the LUMO of the [Pt(x,x′-(NO2)2-bipy)Cl2] 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.
我们报告了一系列一硝基和二硝基取代的 2,2′-联吡啶(bipy)化合物[x-NO2-bipy(x = 3、4)和 x,x′-(NO2)2-联吡(x,x′ = 3, 4, 5)] 及其与铂(II)的配合物 [Pt(x-NO2-bipy)Cl2] 和 [Pt(x,x′-(NO2)2-联吡)Cl2]。在 DFT 计算的支持下,通过原位紫外/可见光/近红外和 EPR 光谱电化学方法,探究了硝基的数量和取代模式对低洼受体分子轨道(参与电荷转移转换)的影响。x-NO2-bipy (x = 3-5)的 LUMOs 大部分位于 NO2-吡啶基上;它们的 PtCl2} 复合物也是如此,但电子密度从硝基上发生了微小但显著的转移。x=3 和 5 时,x,x′-(NO2)2-联吡的 LUMO 在两个 NO2-吡啶环上分散,而 4,4′-(NO2)2-联吡的 LUMO 则集中在单个 NO2-吡啶环上。在所有情况下,[Pt(x,x′-(NO2)2-联吡)Cl2] 复合物的 LUMO 都分散在两个硝基吡啶环上。在所有配合物中,4(4′) 衍生物的 LUMO 与金属价轨道的重叠最大。