A charge transfer state induced by strong exciton coupling in a cofacial μ-oxo-bridged porphyrin heterodimer

Niloofar Zarrabi; Brandon J. Bayard; Sairaman Seetharaman; Noah Holzer; Paul Karr; Susanna Ciuti; Antonio Barbon; Marilena Di Valentin; Art van der Est; Francis D’Souza; Prashanth K. Poddutoori

doi:10.1039/D0CP05783E

A charge transfer state induced by strong exciton coupling in a cofacial μ-oxo-bridged porphyrin heterodimer†

Niloofar Zarrabi,^a Brandon J. Bayard,^a Sairaman Seetharaman,^b Noah Holzer,^a Paul Karr,^c Susanna Ciuti,

^d Antonio Barbon,

^d Marilena Di Valentin,

^d Art van der Est,

*^e Francis D’Souza

*^b and Prashanth K. Poddutoori

*^a

Author affiliations

* Corresponding authors

^a Department of Chemistry & Biochemistry, University of Minnesota Duluth, 1039 University Drive, Duluth, Minnesota 55812, USA
E-mail: ppk@d.umn.edu

^b Department of Chemistry, University of North Texas, 1155 Union Circle, # 305070, Denton, Texas 76203-5017, USA
E-mail: Francis.Dsouza@UNT.edu

^c Department of Physical Sciences and Mathematics, Wayne State College, 111 Main Street, Wayne, Nebraska, USA

^d Dipartimento di Scienze Chimiche, Università degli studi di Padova, Via Marzolo 1, 35131 Padova, Italy

^e Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, Canada
E-mail: avde@brocku.ca

Abstract

Photosensitizers with high energy, long lasting charge-transfer states are important components in systems designed for solar energy conversion by multistep electron transfer. Here, we show that in a push–pull type, μ-oxo-bridged porphyrin heterodimer composed of octaethylporphyrinatoaluminum(III) and octaethylporphyrinatophosphorus(V), the strong excitonic coupling between the porphyrins and the different electron withdrawing abilities of Al(III) and P(V) promote the formation of a high energy CT state. Using, an array of optical and magnetic resonance spectroscopic methods along with theoretical calculations, we demonstrate photodynamics of the heterodimer that involves the initial formation of a singlet CT which relaxes to a triplet CT state with a lifetime of ∼130 ps. The high-energy triplet CT state (³CT = 1.68 eV) lasts for nearly 105 μs prior to relaxing to the ground state.

Physical Chemistry Chemical Physics

A charge transfer state induced by strong exciton coupling in a cofacial μ-oxo-bridged porphyrin heterodimer†

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A charge transfer state induced by strong exciton coupling in a cofacial μ-oxo-bridged porphyrin heterodimer

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