Iron(II) coordination complexes with panchromatic absorption and nanosecond charge-transfer excited state lifetimes

Jason D Braun; Issiah B Lozada; Charles Kolodziej; Clemens Burda; Kelly M E Newman; Johan van Lierop; Rebecca L Davis; David E Herbert

doi:10.1038/s41557-019-0357-z

Iron(II) coordination complexes with panchromatic absorption and nanosecond charge-transfer excited state lifetimes

Nat Chem. 2019 Dec;11(12):1144-1150. doi: 10.1038/s41557-019-0357-z. Epub 2019 Nov 18.

Authors

Jason D Braun¹, Issiah B Lozada¹, Charles Kolodziej², Clemens Burda², Kelly M E Newman³, Johan van Lierop^{3

4}, Rebecca L Davis¹, David E Herbert^{5

6}

Affiliations

¹ Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada.
² Department of Chemistry, Case Western Reserve University, Cleveland, OH, USA.
³ Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada.
⁴ Manitoba Institute for Materials, University of Manitoba, Winnipeg, Manitoba, Canada.
⁵ Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada. david.herbert@umanitoba.ca.
⁶ Manitoba Institute for Materials, University of Manitoba, Winnipeg, Manitoba, Canada. david.herbert@umanitoba.ca.

PMID: 31740761
DOI: 10.1038/s41557-019-0357-z

Abstract

Replacing current benchmark rare-element photosensitizers with ones based on abundant and low-cost metals such as iron would help facilitate the large-scale implementation of solar energy conversion. To do so, the ability to extend the lifetimes of photogenerated excited states of iron complexes is critical. Here, we present a sensitizer design in which iron(II) centres are supported by frameworks containing benzannulated phenanthridine and quinoline heterocycles paired with amido donors. These complexes exhibit panchromatic absorption and nanosecond charge-transfer excited state lifetimes, enabled by the combination of vacant, energetically accessible heterocycle-based acceptor orbitals and occupied molecular orbitals destabilized by strong mixing between amido nitrogen atoms and iron. This finding shows how ligand design can extend metal-to-ligand charge-transfer-type excited state lifetimes of iron(II) complexes into the nanosecond regime and expand the range of potential applications for iron-based photosensitizers.