Electron transfer and solvation in 9,9′-bianthryl and derivatives: a sub-ps fluorescence upconversion study

The time-evolution of the fluorescence spectra of 9,9′-bianthryl and 9-carbazolyl-anthracene in ethanol and butanol have been studied with subpicosecond time-resolution by the fluorescence upconversion technique. For both compounds, an initial phase (<1 ps) with a structured anthracene-type fluorescence spectrum could be observed which transforms into an unstructured redshifted emission spectrum further shifting to the red on the time scale of the slow component of solvent relaxation. The results are compared to recent transient absorption studies and are interpreted as evidence for a subpicosecond relaxation process (ca 0.4 ps) occurring prior to electron transfer in these compounds.