Probing the use of long lived intra-ligand π-π * excited states for photocatalytic systems: a study of the photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)]

Summers, Peter A.; Calladine, James A.; Ibrahim, Nasiru; Kusumo, Kennedy P.; Clark, Charlotte A.; Sun, Xue-Z.; Hamilton, Michelle L.; Towrie, Michael; McMaster, Jonathan; Schr�der, Martin; George, Michael W.

Abstract

We report the excited state photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)] (dppz-(CH3)2 = 11,12-dimethyl-dipyrido[3,2-a:2’,3’-c]phenazine) in CH3CN using timeresolved infrared (TRIR) and Fourier transform infrared (FTIR) spectroscopy. Excitation of the 1MLCT (metal-to-ligand charge transfer) band of [ReCl(CO)3(dppz-(CH3)2)] populates a 3MLCT excited state which rapidly interconverts on a timescale < 1 ns to a long lived IL (intra-ligand) π-π* excited state with a lifetime of 190 (± 5) ns. In the presence of an electron donor (NEt3), the IL excited state of [ReCl(CO)3(dppz-(CH3)2)] can be reductively quenched to [ReCl(CO)3(dppz-(CH3)2)]− with the radical in the latter localised on the distal phenazine (phz) portion of the dppz ligand. The phz based electron in [ReCl(CO)3(dppz-(CH3)2)]− has minimal interaction with the rhenium metal centre which increases the stability of the photosensitiser in its reduced form. In non-dried, non-degassed CH3CN (1 M NEt3), [ReCl(CO)3(dppz-(CH3)2)]− shows no significant change in the carbonyl region of the IR spectrum for at least 2 hours during continuous photolysis. In addition, we investigate the use of [ReCl(CO)3(dppz-(CH3)2)]− to reduce the previously studied catalyst [NiFe2], with facile electron transfer from [ReCl(CO)3(dppz-(CH3)2)]− to form [NiFe2]–.

Citation

Summers, P. A., Calladine, J. A., Ibrahim, N., Kusumo, K. P., Clark, C. A., Sun, X., …George, M. W. (2017). Probing the use of long lived intra-ligand π-π * excited states for photocatalytic systems: a study of the photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)]. Polyhedron, 123, 259-264. https://doi.org/10.1016/j.poly.2016.11.005

• Journal Article Type: Article
• Acceptance Date: Aug 15, 2016
• Online Publication Date: Nov 12, 2016
• Publication Date: Feb 17, 2017
• Deposit Date: Sep 13, 2017
• Publicly Available Date: Sep 13, 2017
• Journal: Polyhedron
• Print ISSN: 0277-5387
• Electronic ISSN: 0277-5387
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 123
• Pages: 259-264
• DOI: https://doi.org/10.1016/j.poly.2016.11.005
• Keywords: Rhenium ; Time-resolved IR ; Photophysics ; Intra-ligand excited state ; Reductive quenching
• Public URL: https://nottingham-repository.worktribe.com/output/845392
• Publisher URL: http://www.sciencedirect.com/science/article/pii/S0277538716305836?via%3Dihub
• Additional Information: This article is maintained by: Elsevier; Article Title: Probing the use of long lived intra-ligand π–π* excited states for photocatalytic systems: A study of the photophysics and photochemistry of [ReCl(CO)3(dppz-(CH3)2)]; Journal Title: Polyhedron; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.poly.2016.11.005; Content Type: article; Copyright: © 2016 Published by Elsevier Ltd.