Novel dodecaarylporphyrins: synthesis and dynamic properties

Magnetic circular dichroism spectroscopy of cobalt tetraphenyltetraacenaphthoporphyrin

“…Shelnutt and coworkers have proposed, based on molecular mechanics and INDO/s calculations, that there is a direct correlation between the red shifts observed for the Q and B bands of sterically hindered porphyrins and the degree of ligand non-planarity [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. On the other hand, Di Magno and coworkers [19][20][21] have pointed to the fact that saddled free base and cobalt tetrakis(perfluoroalkyl)porphyrins do not show a red shift relative to the planar tetraphenylporphyrins and have postulated that red shifts are due to the impact of electron withdrawing or donating effects and in-plane nuclear reorganization induced by bulky substituents on the HOMO-LUMO band gap and the energies of the frontier p-MOs.…”

“…the spectra of highly saddled porphyrinoids. The MCD spectroscopy of the transition metal complexes of sterically hindered synthetic porphyrinoids clearly merits further investigation, since new insights into the biochemical role of non-planar porphyrinoids can be derived using the model compound approach that has been developed in recent years by Shelnutt and coworkers [6][7][8][9][10][11][12][13][14][15][16][17][18].…”

“…There has been considerable recent controversy over the origin of significant red shifts observed in the major p ? p * bands of peripherally crowded dodecasubstituted porphyrins, which have been used to model the effects of ligand folding on the optical spectroscopy and electronic properties of metal porphyrinoids in proteins [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Ligand non-planarity is one of the key factors in determining the redox properties, the basicity of the inner nitrogen atoms, and the axial ligand binding affinity of metal porphyrinoids and is, therefore, believed to play a role in controlling the function of heme proteins, and, in particular, methyl-coenzyme M reductase [6,7].…”

Highly substituted 2,3,7,8,12,13,17,18-octaethylporphyrins with meso aryl residues

“…These are notably upfield shifts of the signals with increasing degree of substitution, 9 NH signals shifted downfield with increasing substitution 18 and in several cases a broadening of the 1 H NMR proton signals at rt was observed. 10b, 19 Porphyrins with larger aromatic residues, e.g., the naphthyl and phenanthrenyl derivatives occurred as mixtures of atropoisomers, due to hindered rotation of the aryl substituents. Detailed NMR spectroscopic investigations 20 were in agreement with earlier reports.…”

Oxygen Activation Chemistry of Pacman and Hangman Porphyrin Architectures Based on Xanthene and Dibenzofuran Spacers

“…Given that the etioporphyrin-type substitution patterns of the parent DPX and DPD systems are generally unstable to oxidizing conditions, owing to the unprotected meso positions on the porphyrin rings, it was reasoned that the construction of meso-substituted bisporphyrin Pacman derivatives might display higher catalase (and more generally, oxidative) efficiencies. Scheme 3 presents a modular and general synthetic route for the facile preparation of mesotetraaryl cofacial bisporphyrins affixed to xanthene (DTMPX ¼ ditrimesitylporitylporphyrin xanthene) or dibenzofuran (DTMPD ¼ ditrimesitylporphyrin dibenzofuran) scaffolds using Suzuki cross-coupling methods (140)(141)(142)(143)(144)(145)(146)(147)(148)(149)(150)(151)(152)(153)(154). The mesityl (mes) substituents incorporated into the Pacman motif provide steric bulk, as well as oxidative stability for high-valent metal oxo species (155,156).…”