EXCITED-STATE SPECTRA AND DYNAMICS OF PHENYL-SUBSTITUTED BUTADIENES

A combination of steady-state and dynamic spectral measurements are us ed to provide new insights into the nature of the excited-state proces ses of all-trans-1,4-diphenyl-1,3-butadiene and several analogs: 1,4-d iphenyl-1,3-cyclopentadiene, 1,1,4,4-tetraphenylbutadiene, 1,2,3,4-tet raphenyl-1,3-cyclopentadiene, and E,E-diindanylidenylethane. Ground-st ate absorption, fluorescence, and nanosecond transient absorption meas urements identify geometry changes upon excitation and provide informa tion regarding the nature of the first excited singlet state. Femtosec ond and picosecond transient absorption data indicate that phenyl tors ional 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 differe nt electronic properties and excited-state dynamics.