Porphyrazines with bulky peripheral pyrrolyl substituents – Synthesis via microwave-assisted Suzuki-Miyaura cross-coupling reaction, optical and electrochemical properties

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Synthesis of novel aminoporphyrazines with peripheral 3,4-dihalide-2,5-dimethylpyrrol-1-yl and dimethylamino peripheral groups is reported. Cross-coupling Suzuki-Miyaura reaction with phenylboronic acid was used to convert magnesium(II) porphyrazine with dimethylamino and 3,4-dibromo-2,5-dimethylpyrrol-1-yl groups to an analogue with bulky 2,5-dimethyl-3,4-diphenylpyrrol-1-yl moieties. Microwave-assisted organic synthesis approaches were used in the Paal-Knorr reaction leading to the modified diaminomaleonitrile intermediates and the Suzuki-Miyaura reaction, which allowed the obtaining of porphyrazine derivative. All compounds were characterized using UV–Vis, 1H and 13C NMR, including 2D techniques, as well as MS (ES or MALDI). An X-ray analysis of magnesium(II) porphyrazine with peripheral 3,4-dibromo-2,5-dimethylpyrrol-1-yl and dimethylamino substituents was also performed. The electrochemical properties of all obtained porphyrazine macrocycles were assessed using cyclic and differential pulse voltammetry. The susceptibility of new macrocycles to oxidation/reduction processes depended on the presence of halide substituents in their macrocyclic periphery.