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Acid-base properties of tetrapyrazinoporphyrazines. 1. Deprotonation ofoctaethyltetrapyrazinoporphyrazine in CH2Cl2, THF, DMSO and pyridine. The crucial role of waterстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 11 ноября 2019 г.
- Авторы: Stuzhin PA, Malyasova AS, Sheinin VB, Kokareva E., TarakanovPA, Koifman OI
- Журнал: Dyes and Pigments
- Том: 139
- Год издания: 2017
- Издательство: Elsevier BV
- Местоположение издательства: Netherlands
- Первая страница: 509
- Последняя страница: 516
- DOI: 10.1016/j.dyepig.2016.12.047
- Аннотация: Combination of experimental and theoretical methods were used to study NH-acidity and related spectral properties of tetrapyrazinoporphyrazines – octaazaanalogues of phtalocyanines. The theoretical values of deprotonation enthalpy (DPE) in gaseous phase indicate that substitution of benzene rings in phthalocyanine by pyrazine fragments strongly enhances the NH-acidity of the macrocycle which can be further tuned by introduction of substituents in pyrazine rings. Spectrophotometric titration study of octaethyl substituted tetrapyrazinoporphyrazine, [Et8TPyzPAH2], in organic solvents (CH2Cl2, THF and DMSO) has revealed that it is easily deprotonated not only in the presence of strong bases such as tetrabutylammonium hydroxide, but also in such proton-acceptor solvent as DMSO. The thermodynamic acidity constants (pKa1 = 7.77 and pKa2 = 7.80) determined for [Et8TPyzPAH2] in DMSO solution using spectropotentiometric titration indicate that TPyzPA macrocycle has ∼ 1000 times stronger NH-acidity than phthalocyanine. Deprotonation of [Et8TPyzPAH2] in pyridine solution is only possible in the presence of water playing a crucial role in formation of the dianion, which can be considered as a sensitive spectral sensor for water traces. Theoretical DFT B3LYB/631++G(p,d) study has confirmed that the dianion is only stabilized as bisaqua complex [TPyzPA(H2O)2]2− with complementary H-bonds between water molecule and N-atoms of two opposite pyrrole rings (N…HOH…N).
- Добавил в систему: Дубинина Татьяна Валентиновна