title: Pivotal Role of a Pentacoordinate (3)MC State on the Photocleavage Efficiency of a Thioether Ligand in Ruthenium(II) Complexes: A Theoretical Mechanistic Study.
abstract: A mechanistic study of the photocleavage of the methylthioethanol ligand (Hmte) in the series of ruthenium complexes [Ru(tpy)(N-N)(Hmte)](2+) (tpy = 2,2':6',2″-terpyridine, N-N = bpy (2,2'-bipyridine), biq (2,2'-biquinoline), dcbpy (6,6'-dichloro-2,2'-bipyridine), dmbpy (6,6'-dimethyl-2,2'-bipyridine)) was performed using density functional theory. These studies reveal the decisive role of two quasi-degenerate triplet metal-centered states, denoted (3)MChexa and (3)MCpenta, on the lowest triplet potential energy surface. It also shows how the population of the specific pentacoordinate (3)MCpenta state, characterized by a geometry more accessible for the attack of a solvent molecule, is a key step for the efficiency of the photosubstitution reaction. The difference in the photosubstitution quantum yields experimentally observed for this series of complexes (from φ = 0.022 for N-N = bpy up to φ = 0.30 for N-N = dmbpy) is rationalized by the existence of this (3)MCpenta photoreactive state and by the different topologies of the triplet excited-state potential energy surfaces, rather than by the sole steric properties of these polypyridinyl ligands.
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, UMR 5626, IRSAMC, CNRS et Université de Toulouse , 118 route de Narbonne, 31062 Toulouse, France.
authors.forename: Adrien J
authors.initials: AJ
authors.lastname: Göttle
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, UMR 5626, IRSAMC, CNRS et Université de Toulouse , 118 route de Narbonne, 31062 Toulouse, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Alary
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, UMR 5626, IRSAMC, CNRS et Université de Toulouse , 118 route de Narbonne, 31062 Toulouse, France.
authors.forename: Martial
authors.initials: M
authors.lastname: Boggio-Pasqua
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, UMR 5626, IRSAMC, CNRS et Université de Toulouse , 118 route de Narbonne, 31062 Toulouse, France.
authors.forename: Isabelle M
authors.initials: IM
authors.lastname: Dixon
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, UMR 5626, IRSAMC, CNRS et Université de Toulouse , 118 route de Narbonne, 31062 Toulouse, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Heully
authors.affiliation: Leiden Institute of Chemistry, Leiden University , Einsteinweg 55, 2333 CC Leiden, The Netherlands.
authors.forename: Azadeh
authors.initials: A
authors.lastname: Bahreman
authors.affiliation: Leiden Institute of Chemistry, Leiden University , Einsteinweg 55, 2333 CC Leiden, The Netherlands.
authors.forename: Sven H C
authors.initials: SH
authors.lastname: Askes
authors.affiliation: Leiden Institute of Chemistry, Leiden University , Einsteinweg 55, 2333 CC Leiden, The Netherlands.
authors.forename: Sylvestre
authors.initials: S
authors.lastname: Bonnet