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[Ru(bipyridine)2(nicotinamide)2]2+ (1) and its monoaqua-complex [Ru(bipyridine)2(nicotinamide)(H2O)]2+ (2) were spectroscopically studied for the first time in the gas phase by static and time resolved UV photodissociation spectroscopy, observing nicotinamide and H2O 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, i.e., exclusive H2O 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 ca. 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 3MC vs. the 3MLCT 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 3MLCT/3MC 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 λ > 550 nm to the 3MC 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. [ABSTRACT FROM AUTHOR]

The molecular structure and pure rotational spectra of two short-lived molecules, the chlorophosphane PH2Cl and the fluorophosphane PH2F, were examined via SCF, MP2, CCSD and CCSD(T) ab initio computations as well as millimeter-wave spectrometry, respectively. The results showed good agreement between observations and ab initio predictions concerning the ground state structural and rotational parameters.

Offset not found [ABSTRACT FROM AUTHOR]

In this work, the X 2B1 and à 2A1 electronic states of the phosphino (PH2) free radical have been studied by dispersed fluorescence and ab initio methods. PH2 molecules were produced in a molecular free-jet apparatus by laser vaporizing a silicon rod in the presence of phosphine (PH3) gas diluted in helium. The laser-induced fluorescence, from the excited à 2A1 electronic state down to the ground electronic state, was dispersed and analyzed. Ten (υ1υ2υ3) vibrationally excited levels of the ground electronic state, with υ1≤2, υ2≤6, and υ3=0, have been observed. Ab initio potential-energy surfaces for the X 2B1 and à 2A1 electronic states have been calculated at 210 points. These two states correlate with a 2Πu state at linearity and they interact by the Renner-Teller coupling and spin-orbit coupling. Using the ab initio potential-energy surfaces with our RENNER computer program system, the vibronic structure and relative intensities of the à 2A1→X 2B1 emission band system have been calculated in order to corroborate the experimental assignments. [ABSTRACT FROM AUTHOR]

The semiempirical OM2/multireference configuration interaction (MR-CIS) level surface-hopping approach is employed to study the nonradiative deexcitation dynamics of 9H-adenine. A two-step relaxation mechanism consisting of an ultrashot component and a longer component is shown to govern the deexcitation process.