Impacts of Ion-Pairing Effects on Linear and Nonlinear Photophysical Properties of Polymethines Dyes

Ion-pairing between cationic heptamethine and small bromine anion in a non-dissociating solvent results in a symmetry breaking towards a dipolar type chromophore, a transition that is never observed in presence of a bulky B(C6F5)4 anion. For the first time, the effects of ion-pairing on the linear and nonlinear photophysical properties is investigated and reveals significant discrepancies between cyanine and dipolar states.