Computational and experimental insights into the oxidative stability of iron porphyrins: A mono‐ortho‐substituted iron porphyrin with unusually high oxidative stability

Abstract

The oxidative stability of iron(III) meso-tetraarylporphyrins in oxidation of styrene with periodate decreased in the order FeT(2-Me)PPOAc > > FeT(2-Cl)PPOAc > FeTPPOAc > FeT(4-OMe)PPOAc. While the observed order correlates approximately with the electron deficiency of the porphyrin ligands, FeT(2-Me)PPOAc showed an unusually high stability (99.1% in 120 minutes) under reaction conditions. It is noteworthy that due to the presence of bulky and electronegative chlorine atoms at the ortho positions of FeT(2-Cl)PPOAc, a higher or at least comparable oxidative stability was expected for FeT(2-Cl)PPOAc. The energy, electronic, and structural features obtained from spin-unrestricted hybrid density functional theorybased calculations showed the involvement of steric and electronic effects as the main factors determining the oxidative stability of iron porphyrins.In the case of FeT(2-Me)PPOAc, the steric bulk of methyl substituents as well as the large dihedral angle between the aryl substituents and porphyrin mean plane seem to play crucial roles in the observed oxidative stability.

Selective Aerobic Oxidation of 4-Ethylnitrobenzene to 4-Nitroacetophenone Promoted by Metalloporphyrins

“…Similar phenomena were also observed in aerobic oxidation promoted by other metalloporphyrins discussed above. Also, the bleach or degradation of the metalloporphyrins in reaction systems was reported by the Cunningham, − Nasrollahi, and Khazaei groups . The composition of the reaction mixture was also confirmed by a UV–vis spectra analysis (Figure ).…”

“…Also, the bleach or degradation of the metalloporphyrins in reaction systems was reported by the Cunningham, 47−49 Nasrollahi, 50 and Khazaei groups. 51 The composition of the reaction mixture was also confirmed by a UV−vis spectra analysis (Figure 7). reletively weak absorption bands for the Q bands at 582 and 617 nm were observed clearly.…”

Significantly Increased Stability of Donor–Acceptor Molecular Complexes under Heterogeneous Conditions: Synthesis, Characterization, and Photosensitizing Activity of a Nanostructured Porphyrin–Lewis Acid Adduct

“…It is noteworthy that because of high oxidizing ability of singlet oxygen, porphyrin macrocycle can be attacked by this species. Although there is little information concerning the oxidative and photooxidative degradation of porphyrins and metalloporphyrins, the carbon atoms with larger electron densities, that is, α, β, and meso-carbons, have been suggested to be involved in the catalyst degradation reactions. , As can be seen from Table , because of high oxidative degradation of the latter after the first use, the catalyst was no longer used for further runs. It is noteworthy that no detectable catalyst degradation was found for the former after at least five successive runs.…”

Manganese porphyrins/mesoporous amberlyst 15 nanocomposites: Robust biomimetic catalysts for aqueous oxidation of olefins

“…[1][2][3][4][5] Also, computational studies were performed to elucidate different aspects of these catalytic systems such as the mechanism of the oxidation reactions, nature, and relative reactivity of the active oxidants involved in the catalytic cycles and effect of peripheral substituents on the oxidative stability of metalloporphyrins. [6][7][8][9] With respect to the significant effects of the peripheral substituents of porphyrin on the catalytic activity of metalloporphyrins and their stability toward oxidative degradation, the first, second, and third generations of porphyrins were synthesized and applied to the catalytic oxidation of organic substrates. [10] Cytochrome P450 (CYP) enzymes are microsomal membranebound proteins with crucial roles in the metabolism of essential substances, foreign compounds such as drugs and chemical carcinogens, industrial environmental pollutants, insecticides, and carcinogens.…”