Nanosecond and picosecond transient absorption studies were carried out on fac-(bpy)Re-I(CO)3(DA)(+) (1), where bpy is 2,2’-bipyridine land DA is the 1,2-diamine-substituted pyridine erythro-1-{p-[4-(pyridyl)methyl]anilino}-2-piperidino- 1,2-diphenylethane. Photoexcitation of the d pi(Re) --> pi* (bpy) metal-to-ligand charge-transfer excited state in 1 initiates the following sequence : (1) forward electron transfer from the 1,2-diamine unit to the photoexcited (bpy)Re(CO)(3)- chromophore to produce the ligand-to-ligand charge transfer (LLCT) state, (bpy(.-))Re-I(CO)(3)(DA(.+)); (2) C-C bond fragmentation of the diamine radical cation unit. Nanosecond transient absorption spectral data indicate that the a-amino radical which is the primary product of the C-C bond fragmentation is produced during the 10 ns laser excitation pulse. Picosecond pump-probe studies of 1 allow direct determination of the kinetics of back electron transfer in the LLCT state (1 x 10(8) s(-1)) and for C-C bond fragmention in the diamine radical cation (3. x 10(8) s(-1)).