A Thorough Understanding of Methylrhodium(III)–Porphyrin Photophysics: A DFT/TDDFT Study

Rhodium-porphyrin complexes are characterised by their ability to activate C-H and C-C bonds and, therefore, find applications in synthesis and catalysis. Axial rhodoporphyrin ligands are susceptible to photodissociation under the influence of light. DFT and TDDFT calculations were performed to investigate the mechanism of photodissociation of the methyl ligand from the methylrhodium(III)-porphyrin complex (MeRhPor). Various photolysis pathways of the rhodium-methyl bond were investigated, including photolysis from states in the Q and Soret bands. Photolysis from triplet states was also considered. Based on the calculations, the most probable mechanism for photodissociation of the methyl ligand was proposed. The methyl-rhodium binding energy in the methylrhodium(III)-porphyrin complex and the energy of formation of the rhodium-porphyrin radical dimer formed by methyl dissociation were also calculated.