Synthesis and characterization of the multi-photon absorption and excited- state properties of a neat liquid 4-propyl 40-butyl diphenyl acetylene†

The synthesis, characterization, and quantitative electronic structure modeling of multi-photon absorption properties of a neat liquid L34 (4-propyl 40-butyl diphenyl acetylene) are reported. The liquid is (linearly) transparent in the visible spectrum, but possesses large two-photon absorption (2PA) and 2PA-induced singlet and triplet excited-state absorption as measured by the Z-scan technique and non-linear transmission measurements using both picosecond and nanosecond pulses. The most dominant contributions to the intensity-dependent non-linear absorption come from the 2PA-induced triplet excited states in the nanosecond time regime. We also present transient absorption spectra of the liquid obtained by nanosecond laser-flash photolysis and compare these results with electronic structure calculations. The energy of the absorption bands, both singlet and triplet are in reasonable agreement with calculations performed with Gaussian 03. The experimentally measured spectra and theoretical electronic structure modeling provide information about the energy levels of the excited states of this liquid, including 2PA and 2PA-induced process that is responsible for its non-linear optical properties.