Effects of coexisting isomers on two-photon absorption of organic molecules in solutions

Isomer-dependent two-photon absorption spectra of organic molecules in solutions have been identified by time-dependent density functional theory calculations. Experimentally observed enhancements in two-photon absorptions of V-shaped hydroxypyrimidine derivatives are not due to the formation of molecular dimers but to mainly the co-occurrence of geometrical isomers. Solvent effects on both one- and two-photon absorption spectra have been carefully examined by using a supermolecular approach in combination with a polarizable continuum model. Special attention has been paid to understand the effects of hydrogen bonds on electronic structure and absorption spectra of these chromophores. Our calculated results are very helpful for understanding the corresponding experimental observations.