title: High-Efficiency Iron Photosensitizer Explained with Quantum Wavepacket Dynamics.
abstract: Fe(II) complexes have long been assumed unsuitable as photosensitizers because of their low-lying nonemissive metal centered (MC) states, which inhibit electron transfer. Herein, we describe the excited-state relaxation of a novel Fe(II) complex that incorporates N-heterocyclic carbene ligands designed to destabilize the MC states. Using first-principles quantum nuclear wavepacket simulations we achieve a detailed understanding of the photoexcited decay mechanism, demonstrating that it is dominated by an ultrafast intersystem crossing from (1)MLCT-(3)MLCT proceeded by slower kinetics associated with the conversion into the (3)MC states. The slowest component of the (3)MLCT decay, important in the context of photosensitizers, is much longer than related Fe(II) complexes because the population transfer to the (3)MC states occurs in a region of the potential where the energy gap between the (3)MLCT and (3)MC states is large, making the population transfer inefficient.
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy of Sciences , P.O. Box 49, H-1525 Budapest, Hungary.|Department of Chemistry, Technical University of Denmark , DK-2800 Kongens Lyngby, Denmark.
authors.forename: Mátyás
authors.initials: M
authors.lastname: Pápai
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy of Sciences , P.O. Box 49, H-1525 Budapest, Hungary.
authors.forename: György
authors.initials: G
authors.lastname: Vankó
authors.affiliation: Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences , P.O. Box 286, H-1519 Budapest, Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Rozgonyi
authors.affiliation: School of Chemistry, Newcastle University , Newcastle upon Tyne NE1 7RU, United Kingdom.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Penfold