Theoretical and experimental investigation of the semiquinone forms of protocatechuic acid. The effect of manganese
Theoretical and experimental investigation of the semiquinone forms of protocatechuic acid. The effect of manganese
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DOI：
10.1016/j.saa.2009.12.025
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发表时间：
2010-03-01
影响因子：
4.4
通讯作者：
Petropouleas, Panayiotis
中科院分区：
文献类型：
--
作者：
Hatzipanayioti, Despina;Petropouleas, Panayiotis
用密度泛函理论（DFT）在B3 LYP/TZVP水平上研究了原儿茶酸（PCA，3，4-dihydroxybenzoic acid，3，4-DHBA）的10种氧化、氧化和二聚形式，计算了它们的结构和光谱参数（电子跃迁、NMR共振）。结合实验结果（在厌氧或有氧环境下）确定了质子化、完全去质子化和/或氧化的五氯苯甲醚半醌的存在条件。已经绘制了含有锰-（PCA-半醌）和水或/和过氧基团的几种能量优化的构象（物种11-16），并且已经在相同的理论水平上计算了它们的结构和光谱性质。与理论结果相一致的实验结果为Mn（II）-和Mn（III）-[PCA-半醌]的存在以及分子氧活化的条件提供了证据。从这些溶液中分离出的两种蓝色固体（17和18）已被表征。元素分析、TGA、IR和ESR光谱支持Mn-2（PCA）（2）（O-2）（OH）（2）（AcO）（ClO 4）（2）（H2O）（3）（17）和Mn-2（PCA）（2）（O-2）（2）（OH）（2）（AcO）H2O（18）的公式。它们在溶液（蓝色溶液）中的ESR光谱几乎相同，表明Mn（IV）的存在。从整个研究过程中，PCA对分子氧的活化，分子氧在锰上的迁移以及金属离子的氧化作用得到了较好的结果。(C)2009 Elsevier B. V.保留所有权利。
Ten oxidized, oxygenated and dimeric forms of protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid, 3,4-DHBA) have been studied using DFT calculations (at the B3LYP/TZVP level of theory) and their structural and spectroscopic parameters (electronic transitions, NMR resonances) have been calculated. Combination with experimental results (under anaerobic or aerobic environment) determines the conditions for the existence of protonated, fully deprotonate and/or oxygenated semiquinones of PCA. Several energy optimized conformers containing manganese-(PCA-semiquinones) and water or/and peroxo-groups have been drawn (species 11-16) and their structural and spectroscopic properties have been calculated at the same level of theory. Experimental parallel to the theoretical results provide evidence for the existence of Mn(II)- and Mn(III)-[PCA-semiquinonel as well the conditions of dioxygen activation. Two of the blue solids (17 and 18) isolated from these solutions, have been characterized. Elemental analyzes, TGA, IR and ESR spectra support the formulation Mn-2(PCA)(2)(O-2)(OH)(2)(AcO)(ClO4)(2)(H2O)(3) (17), and Mn-2(PCA)(2)(O-2)(2)(OH)(2)(AcO)H2O (18). Their ESR spectra, in solution (blue solutions), are almost identical and indicative of Mn(IV) existence. From the whole investigation, the activation of dioxygen by the PCA, its relocation on manganese and the oxidation of the metal ion have been provided. (C) 2009 Elsevier B.V. All rights reserved.