Pivotal Role of a Pentacoordinate 3MC State on the Photocleavage Efficiency of a Thioether Ligand in Ruthenium(II) Complexes: A Theoretical Mechanistic Study

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• 作者：Adrien J. Göttle ; Fabienne Alary ; Martial Boggio-Pasqua ; Isabelle M. Dixon ; Jean-Louis Heully ; Azadeh Bahreman ; Sven H. C. Askes ; Sylvestre Bonnet
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：May 2, 2016
• 年：2016
• 卷：55
• 期：9
• 页码：4448-4456
• 全文大小：437K
• 年卷期：0
• ISSN：1520-510X

文摘

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 ³MC_hexa and ³MC_penta, on the lowest triplet potential energy surface. It also shows how the population of the specific pentacoordinate ³MC_penta 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 ³MC_penta 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.