A First Principles Study on Zinc–Porphyrin Interaction with O₂in Zinc–Porphyrin(Oxygen) Complex

Abstract

We investigate the interaction between zinc-porphyrin and oxygen molecule in zinc-porphy-rin(oxygen) complex using the first principles calculation. At first, we study the electronic and geometric structures of zinc-porphyrin and compare with other metalloporphyrin (metal = Mn, Fe, Co, and Ni). We demonstrate that the electronic structures of zinc-porphyrin are completely different with other metalloporphyrin, therefore its interaction with oxygen molecule is also different. In the ground state, the complex prefers the form 3 ( 1 ZnP-3 O 2 ). The singlet oxygen generation can be accessed through 1 (ZnP-O 2 ) complex. The excited singlet state of the complex prefers the form 1 ( 1 ZnP-1 O 2 ) and allows the interaction between ZnP and O 2 via charge transfer. Furthermore, we construct a mechanism for the quenching of 3 ZnP induced by 3 O 2 where ZnP-O 2 complexes act as the intermediate states.

A Theoretical Study of Ligand Effects on the Electronic Structures of Ligated Zinc Porphyrin using Density Functional Theory

“…Our DFT calculations use B3LYP exchange-correlation functional [25][26][27] and 6-31G(d, p) basis-set (for hydrogen, carbon, nitrogen, and ‰uorine) and LAN2LDZ basis set as the eŠective core potential (for zinc) [28][29][30][31][32][33] . The choice of the exchange-correlation functional and basis sets are based on our previous study 9) , which the calculated geometry structures of metalloporphyrin is in good agreement with experimental data. All the calculated〈S 2 〉values vary by less than 10z of the corresponding ideal values, hence spin contamination was considered to be insu‹cient to aŠect the molecular structure of our current systems 34) .…”

“…These metalloporphyrins are good diatomic molecules adsorber due to the large contribution of the d-electrons of metal atoms to the lowest unoccupied molecular orbitals (LUMO) and the highest occupied molecular orbitals (HOMO) of metalloporphyrin 7,8) . In contrast, d-electrons of Zn contribute less to LUMO and HOMO of ZnP hence it is an ine‹cient diatomic molecules adsorber 9) .…”

“…The Q-band peak wavelength (l max, Q ) of ZnP depends on the ligation with other molecule. For example, in the same environment, l max, Q of zinc meso-tetraphenylporphyrin (ZnTPP) is longer than that of zinc tetrabenzoporphyrin (ZnTBP), while combining tetraphenyl and tetrabenzo ligands (zinc meso-tetraphenyltetrabenzoporphyrin (ZnTPTBP)) shifts the peak positions in wavelength toward blue region with respect to l max, Q of ZnTBP [9][10][11][12][13] . The red-shifting of ZnTPP's Q-band peak is also observed in axial ligation (formingˆve-coordination zinc complex) [16][17][18] .…”

A Density-Functional Study on the Change of Q/B-Band Intensity Ratio of Zinc Tetraphenylporphyrin in Solvents

“…Both electronic and geometric structure are obtained by DFT with B3LYP exchange-correlation functional 28) and 6-31G(d,p) basisset [29][30][31][32][33][34][35][36][37] (for hydrogen, carbon, nitrogen, and fluorine) and LanL2DZ basis set as the effective core potential [38][39][40][41] (for zinc) which are implemented in Gaussian09 suite program. 42) The choice of the exchange-correlation functional and basis sets are based on our previous study, 27) which the calculated geometry structures of metalloporphyrin are in good agreement with experimental data.…”

“…Our previous works 10,27) suggest that HOMO-HOMO¹1 energy difference of ligated ZnPs [ZnTPP, ZnTBP, zinc tetraphenyltetrabenzoporphyrin or ZnTPTBP, and ZnTPP with axial imidazole ligand or ZnTPP(Im)] that are calculated by DFT are wider than non-ligated one. While in non-ligated ZnP these two orbital has 0.04 eV energy difference, in ZnTPP it is 0.19 eV, and it is wider than ZnTBP, ZnTPTBP and ZnP(Im).…”