Kinetic study of Bodipy resistance to acids and alkalis: Stability ranges in aqueous and non-aqueous solutions

The regularities of the kinetic stability of 4,4-difluoro-4-boradiaza-s-indacene (Bodipy) complexes with alkyl and sulfonic substituents to acids and alkalis in aqueous and non-aqueous media were investigated. Bodipy is super resistant to acids in comparison with complexes of d-metals. The rate of dissociation reaction increases with the increasing of protonating mixtures acidity and decreasing of effective charges on ligand nitrogen atoms, the dissociation of the complexes taking place in accordance with the kinetic equation of the second order. A kinetic model of the process was proposed. Kinetic and activation parameters of studied reactions were determined. Using the quantum chemical calculations it was shown that the interactions of acidic protons with fluorine atoms of complex are energetically preferable at the initial stage of Bodipy dissociation than interactions of protons with the nitrogen atoms of ligand. Increasing pH leads to the growth of Bodipy destruction rate. The first step in this case is the alkaline hydrolysis of the complex coordination center. The decay of the ligand anion to mono pyrrolic products occurs at the next stage. Diagrams of transformations corresponding to the experimentally determined rate equation are proposed. (C) 2013 Elsevier B.V. All rights reserved.