Redox Activity of Electronically Excited Phosphorus Corroles with Axial Chalcogenation

Ground and excited-state redox potentials of a few axially chalcogenated phosphorus-corroles (XPC; XO, S, Se) are reliably obtained using the range-separated hybrid density functional theory in acetonitrile.

Quest for visible-light absorbing metal-free corroles is of increased research interest for both electrocatalytic and photocatalytic applications among others. To this direction, phosphorus corrole (PC) and its functional derivatives hold great potential. In this study, the ground- and excited-state redox properties of PC and its several axially chalcogenated derivatives (XPC; XO, S, Se) are investigated using optimally tuned range-separated hybrid combined with polarizable continuum model for accounting of solvent effects. All XPCs are confirmed to be dynamically stable from normal-mode analysis and also found to possess similar Gibbs free energy changes for their synthesis from the parent freebase corrole. Calculated ground-state (S0) redox potentials indicate corrole-centered reduction and oxidation for all the studied molecules. While the nature of the chalcogen only marginally influences the lowest excited singlet (S1) and triplet (T1) states including the contributing frontier molecular orbitals, the excited-state photodynamics are greatly affected by the chalcogenation leading to chalcogen-dependent access to either S1/T1 for redox processes. A qualitatively similar trend is observed in S0 and S1/T1-state redox potentials, albeit of markedly different values. These findings contribute valuable insights for the development of next-generation energy-efficient electrocatalysts and photocatalysts utilizing metal-free, visible-light absorbing corrole macrocycles.

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