Thermochromism and solvatochromism of bis[1,2-bis(3,4-di-n-alkoxyphenyl)ethanedione dioximato]nickel(II) complexes

Abstract

The long-alkoxy-chain substituted bis(glyoximato)nickel(II) complexes, bis[1,2-bis(3,4-di-n-alkoxyphenyl)ethanedione dioximato]nickel(II)(n-alkoxy =n-C₈H₁₇O₁n-C₁₂H₂₅O), exhibit ‘mesomorphic thermochromism’ and solvatochromism. The effect of temperature and polarity of the solvent on electronic spectra of these complexes has been investigated. It was found that the thermochromism and the solvatochromism are due to the 3d_z²–4p_z interband transition, which is sensitive to the one-dimensional Ni–Ni stacking distance. This transition shifts to higher energy with increasing temperature. It is closely correlated to aggregation of these complexes both in the mesophase and in solution.