Excited State Spectra and Dynamics of Phenyl-Substituted Butadienes

A combination of steady-state and dynamic spectral measurements are used to provide new insights into the nature of the excited-state processes of all-trans-1,4-diphenyl-1,3-butadiene and several analogs: 1,4-diphenyl- 1,3-cyclopentadiene, 1,1,4,4-tetraphenylbutadiene, 1,2,3,4-tetraphenyl-1,3-cyclopentadiene, and E,E-diindanylidenylethane. Ground-state absorption, fluorescence, and nanosecond transient absorption measurements identify geometry changes upon excitation and provide information regarding the nature of the first excited singlet state. Femtosecond and picosecond transient absorption data indicate that phenyl torsional motion is not important to the excited-state dynamics and reveal alternative excited-state reaction pathways. The results demonstrate how molecular systems that are structually similar can exhibit different electronic properties and excited-state dynamics.