More light on the low electronic transition energy bands of dithizone

Abstract

The visible electronic spectral behaviour of different concentrations of dithizone in pure and mixed various organic solvents has been investigated. It is identified that in dilute basic solvents solutions, dithizone (H 2DZ) exists mainly in monovalent anionic form (HDZ −), where its extent of ionization is largely dependent on the solvent basicity effect. The visible absorption band belonging to absorption of HDZ − form and the shorter visible one belonging to absorption of H 2DZ form are assigned to a transition involving the whole solute associated with intramolecular CT interaction. On the other hand, the longer wavelength visible band observed in the spectrum of the H 2DZ form is assigned to absorption of hydrogen bonding solvated molecular complex. This involves an electron transfer from the lone pair of electrons belonging to solvent molecule to the σ*-antibonding orbital of the acidic NH bond belongs to H 2DZ form.