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Picosecond Metal-to-Ligand Charge-Transfer Deactivation in Co(ppy)3 via Jahn-Teller Distortion
Justin T Malme1, Jenelle N Weaver1, Gregory S Girolami1
1Department of Chemistry, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States.
Abstract:
The excited-state dynamics of fac-Co(ppy)3, where ppy = 2-[2-(pyridyl)phenyl], are measured with femtosecond UV-vis transient absorption spectroscopy. The initial state is confirmed with spectroelectrochemistry to have significant metal-to-ligand charge transfer (MLCT) character, unlike other Co complexes that generally have ligand-to-metal charge transfer or ligand-field transitions in this energy range. Ground-state recovery occurs in 8.65 ps in dichloromethane. Density functional theory calculations show that the MLCT state undergoes Jahn-Teller distortion and converts to a five-coordinate triplet metal-centered state in which one Co-N bond is broken. The results highlight a potential pitfall of heteroleptic bidentate ligands when designing strong-field ligands for transition-metal chromophores.
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