T1, T2 state energies and electron affinities of small α,ω-diphenylpolyenes investigated by anion photodetachment photoelectron spectroscopy and excited-state theory

摘要

Photodetachment photoelectron spectroscopy (PD-PES) on molecular radical anions provides electron affinities and direct spectroscopic access to the lowest triplet states T1 and T2 of the corresponding neutral molecules. Herein, we apply this method to investigate trans-stilbene (SB), all-trans-1,4-diphenyl-1,3-butadiene (DPB), and all-trans-1,6-diphenyl-1, 3,5-hexatriene (DPH). Our gas-phase T1 energies agree with previous measurements on condensed crystals. The T2 state energies are determined in this work for the first time. Experimental electron affinities, neutral excited-state transition energies and intensities are compared to theoretical data calculated by using DFT (ground states) or DFT/MRCI (excited states) methods. We give an explanation why intersystem crossing is of minor importance in all three compounds although the T2 states are situated close below the S1 states. Triplet states illuminated: Photodetachment photoelectron spectroscopy on molecular radical anions provides electron affinities and direct access to the triplet states T1 and T 2 of the corresponding neutral molecules. Herein, the method is applied to trans-stilbene (see picture), all-trans-1,4-diphenyl-1,3-butadiene, and all-trans-1,6-diphenyl-1,3,5-hexatriene.