Recently, novel iron-N-heterocyclic carbene complexes have exhibited remarkable 100-fold increases of the lifetime compared to previously known iron(II)-complexes. The usefulness of these promising Fe(II) complexes for light harvesting applications depends critically on the energy and lifetime of the <sup>3</sup>MLCT excited state, as well as the alignment of the excited state to relevant electron acceptors and redox recovery mediators. Each new complex studied experimentally is costly and time consuming, ideally computational methods are a useful screening tool. Recent efforts to investigate excited state effects beyond the Franck–Condon region included unrestricted density functional theory (uDFT) optimizations of relevant minima and construction of projected potential energy surfaces as well as uDFT and time dependent (TD) DFT calculated potential energy surfaces of the lowest triplet state, provide information about activated decay pathways after the initial photexcitation. Here, focusing on the special electronic structure of iron(II)-carbene complexes in the ground and relaxed excited states, allows us to definitively assign states observed in time-resolved optical and X-ray spectroscopy.

Unique electronic structure of iron carbene photosensitizers

254th National Meeting (2017)

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