DFT Study on Structural Distortion and Vibronic Coupling of Vanadyl Porphyrin Anion and Cation

Abstract

The geometries of one-electron reduced/oxidized species ([TOP] − /[VOP] +) of vanadyl porphyrin (VOP) have been calculated with PBE1PBE method. The results show that for both [VOP] − and [VOP] + the ground states are triplet, in which one of the two unpaired electron occupies the d xy orbital of the V atom while the other occupies the π-orbital of porphyrin ring. Thus both [VOP] − and [VOP] + can be considered as π-radicals. The ground state of neutral VOP molecule is doublet with the unpaired electron occupying d xy orbital of V atom. In contract to the C 4v symmetry of neutral VOP molecule, [VOP] − anion has a "rectangular" distorted C 2v structure due to Jahn-Teller effect. The linear vibronic coupling constants for the Jahn-Teller active modes of [TOP] − were evaluated and the node patterns of frontier KS orbitals are used to explain the reason why the distortion occurs along specific modes. The ground state [VOP] + has a porphyrin ring with pronounced bond length alternation due to pseudo-Jahn-Teller effect, causing its symmetry declined from C 4v to C 4. The bond length alternation is well explained with the node patterns of reconstructed frontier KS orbitals.

Solid State Structure, and Optical and Magnetic Properties, of Free Base Tetra(4-pyridyl)porphyrin {H2T(4-Py)P}•– Radical Anions

“…Rectangular deformation of TPP •3– radical trianions was confirmed experimentally for {Al III (THF) 2 (TPP •3– )} . The alteration of the bonds, which is characteristic of rectangular deformations, corresponds well to that of the bonds observed in our case for H 2 T­(4-Py)­P •– .…”

“…All of these distortions decrease the symmetry of the macrocycle from C 4 v to C 2 v but are characterized by different bond structures . Rectangular deformation of TPP •3– radical trianions was confirmed experimentally for {Al III (THF) 2 (TPP •3– )} . The alteration of the bonds, which is characteristic of rectangular deformations, corresponds well to that of the bonds observed in our case for H 2 T­(4-Py)­P •– .…”

“…These show that rectangular or rhombic distortions can occur in porphyrin radical trianions. All of these distortions decrease the symmetry of the macrocycle from C 4 v to C 2 v but are characterized by different bond structures . Rectangular deformation of TPP •3– radical trianions was confirmed experimentally for {Al III (THF) 2 (TPP •3– )} .…”

“…Previously, the Jahn–Teller deformation of the TPP •3– macrocycle in vanadyl porphyrin radical anions {V IV O­(TPP •3– )} was predicted using DFT calculations . These show that rectangular or rhombic distortions can occur in porphyrin radical trianions.…”

Dianionic Titanyl and Vanadyl (Cation+)2[MIVO(Pc4−)]2− Phthalocyanine Salts Containing Pc4− Macrocycles

“…[21,23,24] It is interesting that such ad istortion is almost absent in the dianionic[ FePc] 2À specieso wing to the fact that the reduction in this case is mainly centered on the iron atom. [27,34] Jahn-Teller effects can additionally distort the Pc macrocycles [21,[35][36][37][38] as they are significant in the [e g (p*)] 2 dianion ground state. [28] The distortion of the Pc macrocycle upon reductionc an be explained also in terms of aromaticity.T he Pc 2À macrocycle has astable aromatic 18 p-electron system.The formation of the less stable 19 p-electron system in PcC 3À and the Table 3.…”