Syntheses and Structures of Zwitterionic Indium(III) and Di-zinc Compounds of an Extended Nitrogenous Ligand. Examples of Unusually Long Wavelength Transitions in d¹⁰-Metal Complexes

In acetonitrile, the reaction of hydrated InCl3 and 2-[(2-(pyridylamino)phenylazo]pyridine [HL] affords an ink-blue octahedral indium(III) complex having the formula [InCl3(HL)]. The compound is a zwitterion in which the positive and the negative charges reside on the extended ligand HL. The secondary amine nitrogen in it is deprotonated, while the free pyridyl nitrogen is protonated. The reaction of ZnCl2, on the other hand, produces a di-metallic complex, [Zn2Cl2L2], where the two metal ions are bridged across the deprotonated ligand [L]-. The color of the di-zinc complex is also ink blue. Interestingly, the UV−vis spectrum of the indium compound is almost identical to that of the di-zinc compound. Long-wavelength transitions near 590 nm in these examples are assigned to intraligand π−π* transitions.在乙腈 (acetonitrile) 溶剂中，水合氯化铟(III)与2-[(2-吡啶氨基)苯偶氮]吡啶[HL]发生反应，得到分子式为[InCl₃(HL)]的墨蓝色八面体构型铟(III)配合物。该化合物为两性离子 (zwitterion)，其正负电荷均分布于拓展配体HL之上。其中的仲胺氮发生去质子化，而游离吡啶氮则被质子化。与之相对，氯化锌的反应产物为双核金属配合物[Zn₂Cl₂L₂]，两个金属离子通过去质子化配体[L]⁻桥联。该双核锌配合物同样呈墨蓝色。值得注意的是，该铟配合物的紫外-可见光谱 (UV−vis spectrum) 与双核锌配合物几乎完全一致。上述体系中位于590 nm附近的长波跃迁被归因为配体内π-π*电子跃迁 (intraligand π−π* transitions)。