Highly Nonplanar, Electron Deficient, N-Substituted tetra-Oxocyclohexadienylidene Porphyrinogens:  Structural, Computational, and Electrochemical Investigations

• Published in: Journal of organic chemistry Vol. 69; no. 18; pp. 5861 - 5869
• Main Authors: Hill, Jonathan P, Hewitt, Ian J, Anson, Christopher E, Powell, Annie K, McCarty, Amy Lea, Karr, Paul A, Zandler, Melvin E, D'Souza, Francis
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 03.09.2004; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Organic chemistry; Physical Sciences; Preparations and properties; Science & Technology; FACILE AERIAL OXIDATION; EXPANDED PORPHYRIN; 3,5-DI-TERT-BUTYL-4-HYDROXYPHENYL; ARYL PORPHYRINS; SYSTEMS; DEVICES; INFORMATION-STORAGE; DENSITY FUNCTIONAL CALCULATIONS; PHENOLIC PORPHYRINS; TETRAPHENYLPORPHYRIN; MO method; Electrochemical analysis; Radical cation; Cyclohexane derivatives; Frontier orbital; Molecular structure; Ab initio method; Quinone; Theoretical study; Ketone; Alkylation; Macrocycle; Unsaturated compound; Benzylic compound; Porphyrin; Density functional method; Radical anion; Conjugated compound
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo049401d

The structures and electrochemistry of N-benzylated meso-tetrakis (3,5-di-tert-butyl-4-oxo-cyclohexa-2,5-dienylidene) porphyrinogens have been investigated. Structural determinations reveal the isomeric identity of the products obtained from the N-alkylation of the parent meso-tetra (oxo-cyclohexadienylidene) porphyrinogen. The compounds are subject to increased macrocyclic deformations upon increasing N-substitution culminating in the tetra-N-benzyl derivative, which has a buckling superimposed on the already highly puckered macrocycle. The electrochemical analyses emphasize the electron deficiency of the N-benzylated meso-tetra(oxo-cyclohexadienylidene) porphyrinogens and indicate that they can be considered as quinones conjugated via the unsaturated tetrapyrrolic macrocycle. The N-benzylated compounds studied form stable and well-defined π-cation radical and π-anion radical species because of their highly conjugated nature. Ab initio molecular orbital calculations at the B3LYP/3-21G(*) level confirmed the high degree of conjugation between tetrapyrrole and meso substituents and also gave good agreement between calculated and experimentally determined HOMO−LUMO band gap energies.