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Tuning the excited-state deactivation pathways of dinuclear ruthenium(ii) 2,2′-bipyridine complexes through bridging ligand design

par Elias, Benjamin ;Cerfontaine, Simon;Troian Gautier, Ludovic ;Wehlin, Sara S.A.M.;Loiseau, Frédérique
Référence Dalton transactions, 49, 24, page (8096-8106)
Publication Publié, 2020-06

Article révisé par les pairs

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Résumé :

A detailed photophysical investigation of two dinuclear ruthenium(ii) complexes is reported. The two metallic centers were coordinated to a bis-2,2′-bipyridine bridging ligand, connected either through the para (Lp, Dp) or the meta position (Lm, Dm). The results obtained herein were compared to the prototypical [Ru(bpy)3]2+ parent compound. The formation of dinuclear complexes was accompanied by the expected increase in molar absorption coefficients, i.e. 12 000 M-1 cm-1, 17 000 M-1 cm-1, and 22 000 M-1 cm-1 at the lowest energy MLCTmax transition for [Ru(bpy)3]2+, Dm and Dp respectively. The Lp bridging ligand resulted in a ruthenium(ii) dinuclear complex that absorbed more visible light, and had a longer-lived and more delocalized excited-state compared to a complex with the Lm bridging ligand. Variable temperature measurements provided valuable information about activation energies to the uppermost 3MLCT state and the metal-centered (3MC) state, often accompanied by irreversible ligand-loss chemistry. At 298 K, 48% of [Ru(bpy)3]2+∗ excited-state underwent deactivation through the 3MC state, whereas this deactivation pathway remained practically unpopulated (<0.5%) in both dinuclear complexes. This journal is