ULTRAFAST ELECTRONIC DEACTIVATION AND VIBRATIONAL DYNAMICS OF PHOTOEXCITED URANIUM(IV) PORPHYRIN SANDWICH COMPLEXES

The ground- and excited-state optical spectra of two U(IV) bis(porphyr in) sandwich complexes reveal features characteristic of porphyrins he ld within van der Waals contact. The photoexcited complexes exhibit ul trafast (approximately 1 ps) deactivation to the ground electronic sta te in a multistep process involving intersystem crossing into the trip let manifold and subsequent relaxation via ligand-field (ff) excited s tate(s). This ultrafast and highly energetic electronic deactivation i s followed by complex time-dependent spectral changes on the picosecon d time scale that are ascribed to vibrational relaxation in the ground electronic state.