The Influence of Bromine Substituent on Optical Properties of Some 1,3-Dithiolium Derivatives

Mesoionic 2-(2-(dialkylamino)-1,3-dithiol-2-ylium-4-yl)phenolates bearing two bromine substituents on the phenolate moiety have been obtained by the heterocondensation of the corresponding phenacyl carbodithioates. These compounds have been investigated in terms of the influence of bromine substituents on the optical properties of this type of mesoionic phenolates. The bromine substituents were found to induce a negative solvatochromism and a batochromic shift of the long-wavelenght, solvent dependent, absorption band. In polar solvents, 4-(3,5-dibromo-2-hydroxyphenyl)-2-dialkylamino-1,3-dithiol-2-ylium perchlorates have been found to be in equilibrium with the corresponding mesoionic phenolates.