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

Abstract

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.