Free radicals of phenothiazine and related compounds. IV. Phenothiazinyl‐ and Diphenothiazine‐ Copper Complexes as intermediates and products in the interaction of phenothiazines with copper(II) halides
Abstract:Freie Radikale des Phenothiazins und ähnliche Verbindungen. IV. Phenothiazinyl‐ und Diphenothiazin‐Kupferkomplexe als Zwischen‐ und Endprodukte in der Reaktion von Phenothiazin mit Kupfer (II)‐halogeniden
Darstellung und Eigenschaften einiger Komplexverbindungen des 10‐Phenothiazinylradikals und deren Dimerisierungsprodukte mit Cu(I)‐ und Cu(II)‐ionen werden beschrieben.
Ein Mechanismus für die selektive Chlorierung von Phenothiazinen in Position 1 mittels CuCl2 wird diskutiert. Die Möglichkeit ähnlicher Bromi… Show more
“…To the best of our knowledge, compounds containing a dithia-diazo perylene core as in structure 4 have not been reported in the literature before. Interestingly, three unusual dimers of phenothiazine with N-N-, C 3 -N-, and C 1 -N- connectivity have been reported by Diudea and Silberg formed upon mild oxidation of phenothiazine with copper(II) chloride, i.e., under very mild oxidizing conditions and obviously in the coordination sphere of a transition metal. These peculiar dimerizations can be obviously accounted for by the ease of oxidation and the relative stability of the phenothiazinyl radical cation.…”
Phenothiazine is coupled under Buchwald-Hartwig conditions with bromo anthracenes and perylene as substrates to give phenothiazine-anthracene and phenothiazine-perylene dyads and triads. Investigation of the electronic properties of these sterically demanding N-aryl phenothiazines by absorption and emission spectroscopy, cyclic voltammetry, and DFT calculations revealed that the individual chromophores are decoupled in the electronic ground state but show unique electronic communication in the excited state. For the anthracenyl-bridged diphenothiazine an intense electronic coupling of the phenothiazinyl units is detected upon oxidation. Besides, attempts to synthesize phenothiazine compounds with even more sterically demanding aryl substituents in the 10-position under N-arylation conditions gave rise to the formation of quite unexpected products of arylation and/or oxidative coupling. The folding angle of the phenothiazine in a consanguineous series correlates well with the first oxidation potential.
“…To the best of our knowledge, compounds containing a dithia-diazo perylene core as in structure 4 have not been reported in the literature before. Interestingly, three unusual dimers of phenothiazine with N-N-, C 3 -N-, and C 1 -N- connectivity have been reported by Diudea and Silberg formed upon mild oxidation of phenothiazine with copper(II) chloride, i.e., under very mild oxidizing conditions and obviously in the coordination sphere of a transition metal. These peculiar dimerizations can be obviously accounted for by the ease of oxidation and the relative stability of the phenothiazinyl radical cation.…”
Phenothiazine is coupled under Buchwald-Hartwig conditions with bromo anthracenes and perylene as substrates to give phenothiazine-anthracene and phenothiazine-perylene dyads and triads. Investigation of the electronic properties of these sterically demanding N-aryl phenothiazines by absorption and emission spectroscopy, cyclic voltammetry, and DFT calculations revealed that the individual chromophores are decoupled in the electronic ground state but show unique electronic communication in the excited state. For the anthracenyl-bridged diphenothiazine an intense electronic coupling of the phenothiazinyl units is detected upon oxidation. Besides, attempts to synthesize phenothiazine compounds with even more sterically demanding aryl substituents in the 10-position under N-arylation conditions gave rise to the formation of quite unexpected products of arylation and/or oxidative coupling. The folding angle of the phenothiazine in a consanguineous series correlates well with the first oxidation potential.
The main products of the thermal‐oxidative degradation of p, p'‐di‐tert‐ octyldiphenylamine, phenothiazine and 3,7‐di‐tert‐octylphenothiazine (DODPA/PTZ/DOPTZ) in pentaerythritol ester at 200°C were isolated and identified. Recombination o f aminyl radicals giving various dehydrodimers and dehydro‐trimers is obviously the dominating reaction in the primary stage of antioxidant depletion during ageing of inhibited ester oils. Minor degradation products include quinone imines, quinones, sulphoxides, phenoxazine and phenoxazone derivatives. Because of the complexity of the reactions product analyses are inevitably incomplete.
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