The Cationic Halochromism of Phenolate Betaines: Molecular Dynamics and Quantum Mechanics Studies

M. Domínguez and M. Caroli Rezende*

Facultad de Química y Biología, Universidad de Santiago, Casilla 40, Correo 33, Santiago, Chile

The cationic halochromism of phenolate betaines was reproduced with the aid of a simple theoretical model, by calculation of the longest wavelength transition energies of supermolecules obtained by positioning a cation Mⁿ⁺ at a variable distance from the oxygen atom of the dye.The theoretical results were compared with experimental data for three systems, Reichardt’s betaine 1, Brooker’s merocyanine 2 and the N-methyl-8-oxyquinolinium dye 3. The model was validated by molecular dynamics simulations of solutions of dye 3, in methanol and DMSO, in the presence of variable concentrations of Na⁺.

Keywords: Cationic halochromism, Solvatochromic betaines, Molecular dynamics simulation, Theoretical calculations