The complexes [Ru(tBu2bipy)(bpym)X2] (X = Cl, NCS) and [M(tBu2bipy)2(bpym)][PF6]2 (M = Ru, Os) all have a low-energy LUMO arising from the presence of a 2,2â²-bipyrimidine ligand, and consequently have lower-energy 1MLCT and 3MLCT states than analogous complexes of bipyridine. The vacant site of the bpym ligand provides a site at which Ln(diketonate)3} units can bind to afford bipyrimidine-bridged dinuclear RuâLn and OsâLn dyads; four such complexes have been structurally characterised. UV/Vis and luminescence spectroscopic studies show that binding of the Ln(III) fragment at the second site of the bpym ligand reduces the 3MLCT energy of the Ru or Os fragment still further. The result is that in the dyads [Ru(tBu2bipy)X2(µ-bpym)Ln(diketonate)3] (X = Cl, NCS) and [Os(tBu2bipy)2(µ-bpym)Ln(diketonate)3][PF6]2 the 3MLCT is too low to sensitise the luminescent f-f states of Nd(III) and Yb(III), but in [Ru(tBu2bipy)2(µ-bpym)Ln(diketonate)3][PF6]2 the 3MLCT energy of 13â500 cmâ1 permits energy transfer to Yb(III) and Nd(III) resulting in sensitised near-infrared luminescence on the microsecond timescale.
[Ru(tBu2bipy)(bpym)X2](X = Cl、
NCS)和[M(tBu2bipy)2(bpym)][PF6]2(M = Ru、Os)复合物都具有因 2,2â²-联
嘧啶配体的存在而产生的低能 LUMO,因此其 1MLCT 和 3MLCT 状态的能量低于联
吡啶的类似复合物。bpym
配体的空位提供了一个Ln(二
酮酸)3}单元可以结合的位点,从而产生双
嘧啶桥接的双核 RuâLn 和 OsâLn 二元体;已经对四个这样的配合物进行了结构表征。紫外/可见光和发光光谱研究表明,Ln(III) 片段与 bpym
配体第二个位点的结合进一步降低了 Ru 或 Os 片段的 3MLCT 能量。结果是,在[Ru(tBu2bipy)X2(µ-bpym)Ln(diketonate)3](X = Cl,
NCS)和[Os(tBu2bipy)2(µ-bpym)Ln(diketonate)3][PF6]2 的二元化合物中,3MLCT 太低,无法敏化 Nd(III)和 Yb(III)的发光 f-f 态、但在[Ru(tBu2bipy)2(µ-bpym)Ln(diketonate)3][PF6]2 中,13â500 cmâ1 的 3MLCT 能量允许能量转移到
镱(III)和
钕(III),从而在微秒时间尺度上激发近红外发光。