Density functional theory study on the dynamic Jahn-Teller effect of tetraoxaporphyrin cation and anion radicals

The ground state geometries of tetraoxaporphyrin monocation/monoanion radicals (i.e., [TOP]− and [TOP]+) and their parent neutral molecule (TOP) have been studied with DFT at the B3LYP/6-31G(d) level of theory. It was shown that both [TOP]− and [TOP]+ have planar D2h structures with a rectangular distortion due to the Jahn-Teller (JT) effect. The two conjugated rectangular JT structures can inter-convert dynamically thought a rhombic transition state. The ESR isotropic hyperfine coupling constants on the H atoms (aH) of the radicals were calculated and were found in good agreement with the experiments. The linear vibronic coupling constants were evaluated with DFT calculations, revealing that the B1g modes corresponding to the stretches of the CαCm and CβCβ bonds and the furan symmetric deformation play a critical role in the JT effect of [TOP]− and [TOP]+.