Ultrafast spectroscopy of Ru II polypyridine complexes in the gas phase and the liquid phase: [Ru(2,2'-bipyridine) 2 (nicotinamide) 2 ] 2 .

[Ru(bipyridine)(nicotinamide)] (1) and its monoaqua-complex [Ru(bipyridine)(nicotinamide)(HO)] (2) were spectroscopically studied for the first time in the gas phase by static and time resolved UV photodissociation spectroscopy, observing nicotinamide and HO ligand dissociation for 1 and 2, respectively. Both processes and their ultrafast dynamics were investigated in parallel by transient absorption spectroscopy in aqueous solution. The latter data were newly acquired for the long-wavelength MLCT band excitation of 1 and provide novel ultrafast ligand dissociation results for 2, confirming the gas phase results, , exclusive HO cleavage over nicotinamide loss. Similar apparent time constants in the sub-ps and few ps ranges were obtained for 1 in both phases, whereas a larger time constant of two hundreds of ps for the ground state recovery was observed exclusively in the solution phase. Our reaction scheme accounts for faster dissociation dynamics in the gas phase by energetical lowering of the MC the MLCT states by lack of solvent stabilization of the latter. Based on the apparent time constants, we favour, for the solution dynamics, a fast bimodal vibrational deactivation in the MLCT/MC manifolds and a slow dissociation obfuscated by the ground state recovery. This is substantiated by a similar reaction scheme proposed for the ultrafast dynamics of 2, resulting in a new assignment for transient absorption features with > 550 nm to the MC manifold, and a common kinetic description for 1 and 2. Computations at the TD-DFT/cc-PVTZ/MDF28 level support our spectroscopic findings and the suggested deactivation pathways.