Porphyrin-o-quinones as Model Systems for Electron Transfer and Catecholase Reactions

Abstract

Various porphyrin-o-quinones 1−8 were prepared as model compounds for electron transfer reactions. The synthesis of these compounds could only be accomplished by using oquinone components stabilized by sterically demanding substituents in the o,oЈ-positions and by using protected catechol aldehydes for the initial porphyrin condensation step. The stability of the target compounds strongly depends on the steric influence of substituents on the o-quinone, which are necessary to stabilize the o-quinones. To test this steric influence we synthesized the porphyrin-o-quinones both without and with methyl and tert-butyl groups and investigated the influence of the bridging position on the reactivity. The 1 Hand 13 C-NMR spectroscopic characteristics of all compounds

Unexpected but convenient synthesis of soluble meso-tetrakis(3,4-benzoquinone)-substituted porphyrins

“…Details of the structures as well as the catalytic and magnetic properties of these complexes will be reported later. We note that o-quinones are a versatile starting point for other functionalities including ring-fused or ring-opened products [22,23]. We will also report our investigations of those possibilities in due course.…”

“…Notably, they are o-quinone-substituted porphyrins analogous with those prepared by other workers [21,22,23,29]. Quinone-substituted porphyrins have usually been prepared by synthesis of the porphyrin containing the appropriate oligo-methoxylated compound followed by its demethylation usually employing boron tribromide reagent.…”

Unexpected but convenient synthesis of soluble meso-tetrakis(3,4-benzoquinone)-substituted porphyrins

“…Details of the structures as well as the catalytic and magnetic properties of these complexes will be reported later. We note that o-quinones are a versatile starting point for other functionalities including ring-fused or ring-opened products [22,23]. We will also report our investigations of those possibilities in due course.…”

“…Notably, they are o-quinone-substituted porphyrins analogous with those prepared by other workers [21,22,23,29]. Quinone-substituted porphyrins have usually been prepared by synthesis of the porphyrin containing the appropriate oligo-methoxylated compound followed by its demethylation usually employing boron tribromide reagent.…”

Trans-Disubstituted Tetraarylporphyrin as a Precursor to Larger Molecular Architectures: An Application of MacDonald “2 + 2” Porphyrin Synthesis in Aqueous Anionic Surfactant

“…17,21,22 The demethylation of 2 by BBr 3 produced the corresponding bis(dihydroxyphenyl)porphyrin 4 in 75% yield. Although porphyrin catechols are susceptible to oxidative degradation, 23 this problem was minimized by performing all the purification steps under strongly acidic conditions, thereby keeping the catechol side group less susceptible to oxidation to the corresponding o-quinone, 24 and also diminishing the photosensitization of oxygen by the porphyrin. 25 The acidic condition also kept the porphyrin catechol 4 from binding too tightly to the silica gel chromatographic matrix.…”

The Antioxidant Properties of Asymmetrically Substituted Tetra(meso-aryl)porphyrins with One Phenolic Substituent: The Contribution of Phenol and Porphyrin Fragments to Antioxidant Activity

“…В спектрах ЯМР 1 Н порфиринов 7 и 8 присутствуют сигналы порфи-ринового фрагмента (H β -пиррольных и внутрицикличе-ских NH-протонов) и ароматических заместителей, при-чем соотношение интегральных интенсивностей сиг-налов протонов порфиринового фрагмента и сигналов протонов фенольного фрагмента соответствует одному фенольному фрагменту в молекуле. Строение описанных ранее порфиринов 1-6 подтверждено сопоставлением их спектральных (UV-Vis, ЯМР, масс) характеристик с данными известными из литературы: [23][24][25][26][27] порфирины 1-6 соответствуют заявленной структуре. Спектральные характеристики неописанных ранее порфиринов 7 и 8 аналогичны известным порфиринам 1-6.…”

Unexpected but convenient synthesis of soluble meso-tetrakis(3,4-benzoquinone)-substituted porphyrins

“…Details of the structures as well as the catalytic and magnetic properties of these complexes will be reported later. We note that o-quinones are a versatile starting point for other functionalities including ring-fused or ring-opened products [22,23]. We will also report our investigations of those possibilities in due course.…”

“…Notably, they are o-quinone-substituted porphyrins analogous with those prepared by other workers [21,22,23,29]. Quinone-substituted porphyrins have usually been prepared by synthesis of the porphyrin containing the appropriate oligo-methoxylated compound followed by its demethylation usually employing boron tribromide reagent.…”

Trans-Disubstituted Tetraarylporphyrin as a Precursor to Larger Molecular Architectures: An Application of MacDonald “2 + 2” Porphyrin Synthesis in Aqueous Anionic Surfactant

“…17,21,22 The demethylation of 2 by BBr 3 produced the corresponding bis(dihydroxyphenyl)porphyrin 4 in 75% yield. Although porphyrin catechols are susceptible to oxidative degradation, 23 this problem was minimized by performing all the purification steps under strongly acidic conditions, thereby keeping the catechol side group less susceptible to oxidation to the corresponding o-quinone, 24 and also diminishing the photosensitization of oxygen by the porphyrin. 25 The acidic condition also kept the porphyrin catechol 4 from binding too tightly to the silica gel chromatographic matrix.…”

The Antioxidant Properties of Asymmetrically Substituted Tetra(meso-aryl)porphyrins with One Phenolic Substituent: The Contribution of Phenol and Porphyrin Fragments to Antioxidant Activity

“…В спектрах ЯМР 1 Н порфиринов 7 и 8 присутствуют сигналы порфи-ринового фрагмента (H β -пиррольных и внутрицикличе-ских NH-протонов) и ароматических заместителей, при-чем соотношение интегральных интенсивностей сиг-налов протонов порфиринового фрагмента и сигналов протонов фенольного фрагмента соответствует одному фенольному фрагменту в молекуле. Строение описанных ранее порфиринов 1-6 подтверждено сопоставлением их спектральных (UV-Vis, ЯМР, масс) характеристик с данными известными из литературы: [23][24][25][26][27] порфирины 1-6 соответствуют заявленной структуре. Спектральные характеристики неописанных ранее порфиринов 7 и 8 аналогичны известным порфиринам 1-6.…”

Unexpected but convenient synthesis of soluble meso-tetrakis(3,4-benzoquinone)-substituted porphyrins

“…Details of the structures as well as the catalytic and magnetic properties of these complexes will be reported later. We note that o-quinones are a versatile starting point for other functionalities including ring-fused or ring-opened products [22,23]. We will also report our investigations of those possibilities in due course.…”

“…Notably, they are o-quinone-substituted porphyrins analogous with those prepared by other workers [21,22,23,29]. Quinone-substituted porphyrins have usually been prepared by synthesis of the porphyrin containing the appropriate oligo-methoxylated compound followed by its demethylation usually employing boron tribromide reagent.…”

Trans-Disubstituted Tetraarylporphyrin as a Precursor to Larger Molecular Architectures: An Application of MacDonald “2 + 2” Porphyrin Synthesis in Aqueous Anionic Surfactant

“…17,21,22 The demethylation of 2 by BBr 3 produced the corresponding bis(dihydroxyphenyl)porphyrin 4 in 75% yield. Although porphyrin catechols are susceptible to oxidative degradation, 23 this problem was minimized by performing all the purification steps under strongly acidic conditions, thereby keeping the catechol side group less susceptible to oxidation to the corresponding o-quinone, 24 and also diminishing the photosensitization of oxygen by the porphyrin. 25 The acidic condition also kept the porphyrin catechol 4 from binding too tightly to the silica gel chromatographic matrix.…”

The Antioxidant Properties of Asymmetrically Substituted Tetra(meso-aryl)porphyrins with One Phenolic Substituent: The Contribution of Phenol and Porphyrin Fragments to Antioxidant Activity

“…В спектрах ЯМР 1 Н порфиринов 7 и 8 присутствуют сигналы порфи-ринового фрагмента (H β -пиррольных и внутрицикличе-ских NH-протонов) и ароматических заместителей, при-чем соотношение интегральных интенсивностей сиг-налов протонов порфиринового фрагмента и сигналов протонов фенольного фрагмента соответствует одному фенольному фрагменту в молекуле. Строение описанных ранее порфиринов 1-6 подтверждено сопоставлением их спектральных (UV-Vis, ЯМР, масс) характеристик с данными известными из литературы: [23][24][25][26][27] порфирины 1-6 соответствуют заявленной структуре. Спектральные характеристики неописанных ранее порфиринов 7 и 8 аналогичны известным порфиринам 1-6.…”