DFT Investigation of Ligand Photodissociation in [RuII(tpy)(bpy)(py)]2+ and [RuII(tpy)(Me2bpy)(py)]2+ Complexes
Year: 2017
Type: article
Abstract: Photoinduced ligand dissociation of pyridine occurs much more readily in [Ru(tpy)(Me 2 bpy)(py)] 2+ than in [Ru(tpy)(bpy)(py)] 2+ (tpy = 2,2′:6′,2″-terpyridine; bpy = 2,2′-bipyridine, Me 2 bpy = 6,6′-dimethyl-2,2′-bipyridine; py = pyridine). The S 0 ground state and the 3 MLCT and 3 MC excited states of these complexes have been studied using BP86 density functional theory with the SDD basis set and effective core potential on Ru and the 6-31G(d) basis set for the rest of the atoms. In both complexes, excitation by visible light and intersystem crossing leads to a 3 MLCT state in which an electron from a Ru d orbital has been promoted to a π* orbital of terpyridine, followed by pyridine release after internal conversion to a dissociative 3 MC state. Interaction between the methyl groups and the other ligands causes significantly more strain in [Ru(tpy)(Me 2 bpy)(py)] 2+ than in [Ru(tpy)(bpy)(py)] 2+, in both the S 0 and 3 MLCT states. Transition to the dissociative 3 MC states releases this strain, resulting in lower barriers for ligand dissociation from [Ru(tpy)(Me 2 bpy)(py)] 2+ than from [Ru(tpy)(bpy)(py)] 2+ . Analysis of the molecular orbitals along relaxed scans for stretching the Ru–N bonds reveals that ligand photodissociation is promoted by orbital mixing between the ligand π* orbital of tpy in the 3 MLCT state and the dσ* orbitals that characterize the dissociative 3 MC states. Good overlap and strong mixing occur when the Ru–N bond of the leaving ligand is perpendicular to the π* orbital of terpyridine, favoring the release of pyridine positioned in a cis fashion to the terpyridine ligand.
Source: Inorganic Chemistry
Institutions: Wayne State University, The Ohio State University
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2779945743