Inverse kinetic isotope effect in the excited-state relaxation of a Ru(II)-aquo complex: revealing the impact of hydrogen-bond dynamics on nonradiative decay.
Photophysics of the MLCT excited-state of [Ru(bpy)(tpy)(OH2)](2+) (1) and [Ru(bpy)(tpy)(OD2)](2+) (2) (bpy = 2,2'-bipyridine and tpy = 2,2':6',2″-terpyridine) have been investigated in room-temperature H2O and D2O using ultrafast transient pump-probe spectroscopy. An inverse isotope effect is observed in the ground-state recovery for the two complexes. These data indicate control of excited-state lifetime via a pre-equilibrium between the (3)MLCT state that initiates H-bond dynamics with the solvent and the (3)MC state that serves as the principal pathway for nonradiative decay.
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
Joshua T
JT
Hewitt
Javier J
JJ
Concepcion
Niels H
NH
Damrauer