Tetra chlorocopper(II) chemistry: delineation of optical, thermal properties

The thermal decomposition paths of pyridinium tetra chlorocopper(II) (A) differs from the anilinium tetra chlorocopper(II) (B). In the case of pyridinium tetra chlorocopper(II) it loses two molecules of pyridinium hydrochloride and CuCl₂ is formed in the temperature range of 140–350 °C. Whereas the anilinium tetra chlorocopper(II) (B) loses one mole of anilinum hydrochoride along with one molecule of aniline. The compound B has a well define structural change taking place in the region of 70–110 °C which is reflected in DSC as well as resistance measurements. The p-methoxy anilinium tetra chlorocopper(II) monohydrate (C) shows solvatochromicity. The absorption maximum of p-methoxy anilinium tetra chlorocopper(II)monohydrate in acetonitrile (460 nm) changes to 570 nm on addition of methanol. The absorption at 570 nm can be switched back to 460 nm by suppression of ligand exchange with addition of hydrochloric acid. Thus, chemically driven optical switching properties can be observed.