Solvent Effect and Two-Photon Optical Properties of Triphenylamine-Based Donor–Acceptor Fluorophores
In this work we present a systematic investigation on the optical properties of two triphenylamine (TPA)-based donor–acceptor fluorophores: TPA-PA (phenylaldehyde) and TPA-BMO ((Z)-4-benzylidene-2-methyloxazol-5(4H)-one). The two compounds are dissolved in nine different organic solvents as dilute solutions in order to analyze the effect of solvent on their linear and nonlinear optical properties. For each compound under one-photon excitation, its fluorescence emission spectrum red-shifts more than 160 nm as the solvent polarity increases from hexane to MeCN, while the fluorescence quantum efficiency and lifetime reach maximum magnitudes in solvents with medium polarity. The quantum efficiency reaches as high as 0.72 in dioxane for TPA-PA and 0.69 in Et2O for TPA-BMO, respectively. These TPA-PA and TPA-BMO solutions are also strongly emissive upon appropriate two photon excitation, with fluorescence emission spectra identical to those under corresponding one-photon excitation. The maximum two-photon absor...