The hydrogen-evolving photocatalyst [(tbbpy)2 Ru(tpphz)Pd(Cl)2 ](2+) (tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, tpphz=tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine) shows excitation-wavelength-dependent catalytic activity, which has been correlated to the localization of the initial excitation within the coordination sphere. In this contribution the excitation-wavelength dependence of the early excited-state relaxation and the occurrence of vibrational coherences are investigated by sub-20 fs transient absorption spectroscopy and DFT/TDDFT calculations. The comparison with the mononuclear precursor [(tbbpy)2 Ru(tpphz)](2+) highlights the influence of the catalytic center on these ultrafast processes. Only in the presence of the second metal center, does the excitation of a (1) MLCT state localized on the central part of the tpphz bridge lead to coherent wave-packet motion in the excited state.

Ultrafast intramolecular relaxation and wave-packet motion in a ruthenium-based supramolecular photocatalyst

MAIURI, MARGHERITA;BRIDA, DANIELE;CERULLO, GIULIO NICOLA;
2015-01-01

Abstract

The hydrogen-evolving photocatalyst [(tbbpy)2 Ru(tpphz)Pd(Cl)2 ](2+) (tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, tpphz=tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine) shows excitation-wavelength-dependent catalytic activity, which has been correlated to the localization of the initial excitation within the coordination sphere. In this contribution the excitation-wavelength dependence of the early excited-state relaxation and the occurrence of vibrational coherences are investigated by sub-20 fs transient absorption spectroscopy and DFT/TDDFT calculations. The comparison with the mononuclear precursor [(tbbpy)2 Ru(tpphz)](2+) highlights the influence of the catalytic center on these ultrafast processes. Only in the presence of the second metal center, does the excitation of a (1) MLCT state localized on the central part of the tpphz bridge lead to coherent wave-packet motion in the excited state.
2015
DFT; coherent vibrational motion; photophysics; ruthenium; time-resolved spectroscopy
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/985799
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