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Unusual Reactivity and Metal Affinity of Water-Soluble Dipyrrinsстатья
Статья опубликована в высокорейтинговом журнале
Статья опубликована в журнале из списка Web of Science и/или Scopus- Авторы: El Khatib Mirna, Cheprakov Andrei V., Vinogradov Sergei A.
- Журнал: Inorganic Chemistry
- Том: 61
- Номер: 32
- Год издания: 2022
- Издательство: American Chemical Society
- Местоположение издательства: United States
- Первая страница: 12746
- Последняя страница: 12758
- DOI: 10.1021/acs.inorgchem.2c01834
- Аннотация: Dipyrrins are a versatile class of organic ligands capable of fluorogenic complexation of metal ions. The primary goal of our study was to evaluate dipyrrins functionalized with ester and amide groups in 2,2′-positions in sensing applications. While developing the synthesis, we found that 3,3′,4,4′-tetraalkyldipyrrins 2,2′-diesters as well as 2,2′-diamides can undergo facile addition of water at the meso-bridge, transforming into colorless meso-hydroxydipyrromethanes. Spectroscopic and computational investigation revealed that this transformation proceeds via dipyrrin cations, which exist in equilibrium with the hydroxydipyrromethanes. While trace amounts of acid favor conversion of dipyrrins to hydroxydipyrromethanes, excess acid shifts the equilibrium toward the cations. Similarly, the presence of Zn2+ facilitates elimination of water from hydroxydipyrromethanes with chromogenic regeneration of the dipyrrin system. In organic solutions in the presence of Zn2+, dipyrrin-2,2′-diesters exist as mixtures of mono-(LZnX) and bis-(L2Zn) complexes. In L2Zn, the dipyrrin ligands are oriented in a nonorthogonal fashion, causing strong exciton coupling. In aqueous solutions, dipyrrins bind Zn2+ in a 1:1 stoichiometry, forming mono-dipyrrinates (LZnX). Unexpectedly, dipyrrins with more electron-rich 2,2′-carboxamide groups revealed ∼20-fold lower affinity for Zn2+ than the corresponding 2,2′-diesters. Density Functional Theory (DFT) calculations with explicit inclusion of water reproduced the observed trends and allowed us to trace the low affinity of the dipyrrin-diamides to the stabilization of the corresponding free bases via hydrogen bonding with water molecules. Overall, our results reveal unusual trends in the reactivity of dipyrrins and provide clues for the design of dipyrrin-based sensors for biological applications.
- Добавил в систему: Белецкая Ирина Петровна