Supramolecular solvatochromism. Effect of solvents on the self-assembly and charge transfer absorption characteristics of lipid-packaged, linear mixed-valence platinum complexes

Abstract

Lipid-packaged, mixed-valence linear platinum complexes are dispersed in chloroform, chlorocyclohexane and in methylcyclohexane. They show indigo-colors, which are identical to solid samples. These lipid-complexes display supramolecular thermochromism, resulting from heat-induced dissociation and recovery of coordination chains. Unexpectedly, reassembled samples show altered CT absorption spectra. In chloroform, the reassembled complex gives indigo-color, while the chlorocyclohexane and methylcyclohexane dispersions show blue and red-colors, respectively. These color changes indicate enhanced solvation of lipid-packaged platinum complexes after the heat treatment. The thermal re-assembly also affects the aggregate morphology, and leads to the formation of nanowires, nanofibers and nanoparticles depending on the solvents employed. The conversion of pseudo one-dimensional (1D) inorganic complexes to lipophilic supramolecular assemblies thus gives solvatochromic properties, which are elements not existing in the conventional solid-state inorganic chemistry.