The copper corrole has drawn significant attention due to its unique multiconfigurational electronic structure and saddled geometry in the ground state. Although the ground state of the copper corrole has a saddled, geometry the structure of the first excited state is planar. Additionally, copper corroles are of interest for their ability to catalyze reactions such as the hydrogen evolution reaction and oxygen reduction reactions, but also for medicinal purposes. Specifically, we study tris-meso substituted copper corroles that have played a significant role in catalysis by performing CASPT2 geometry optimizations using both electron donating (-OH, -OCH3, -CH3) and electron withdrawing (-CF3, NO2, -CN) groups. The CASPT2 geometry with a minimal active space (4e,5o) shows that the saddling is increasing from donating to withdrawing groups in the singlet (S0) ground state. In DFT, we see same trend though the magnitude of the change in saddling is more prominent. We also optimized the meso-triphenyl copper corrole complex with the CASPT2 method and obtain geometries is in better agreement with X-ray diffraction compared to DFT. The electronic structure is then further studied on the CASPT2 optimized structure for all of the functionalized corroles using a larger active space, including RASSCF methods. The effect of ligand functionalization on the electronic structure, specifically examining ligand non-innocence, will be discussed.

Electronic structure and molecular geometry of tris-meso substituted copper corroles

ACS Spring 2022

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