Push–pull chromophores: NLO responses, solvatochromism and vibrational spectra in a simple non-perturbative model

The diverse and fascinating properties of push–pull chromophores demonstrate their intrinsic non-linearity, and suggest that standard perturbative approaches are inadequate to describe their behavior. NLO responses of push–pull chromophores are strongly affected by the surrounding and large environmental effects are observed in absorption and emission spectra. Vibrational spectra show impressive dependence on the embedding medium, with unusual inhomogeneous broadening effects appearing in polar solvents. All these seemingly unrelated phenomena are naturally understood based on a simple two-state model self-consistently accounting for the coupling of electrons to molecular vibrations and to the surrounding medium. The few model parameters are extracted from experiment, leading to a simple yet accurate description of the exotic properties of push–pull chromophores.