Two-photon absorption and two-photon excited fluorescence of triphenylamine-based multibranched chromophores

New non-linear optical (NLO) chromophores with triphenylamine as molecular “core” bearing one, two, or three 4-n-butoxystyryl group(s) as molecular branch(es), respectively, have been synthesized and characterized. Pumped by femtosecond laser pulse in 730-870 nm regions, chromophores in solvent exhibit strong two-photon excited fluorescence (TPF) and large two-photon absorption (TPA) cross-section (δTPA) with the increase of molecular branch. Theoretical calculations confirm that the increasing dipole moment difference (Δμge), the decreasing dihedral angle of intramolecular branch segments between S0 and S states, and large excited charge redistribution make molecular δTPA value augment.