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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Resonance Raman Characterization of Different Forms of Ground-State8-Bromo-7-hydroxyquinoline Caged Acetate in Aqueous Solutions
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Resonance Raman Characterization of Different Forms of Ground-State8-Bromo-7-hydroxyquinoline Caged Acetate in Aqueous Solutions

机译：水溶液中不同形式的基态8-溴-7-羟基喹啉笼型乙酸盐的共振拉曼表征

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摘要

The 8-bromo-7-hydroxyquinolinyl group (BHQ) is a derivative of 7-hydroxyquinoline (7-HQ) and BHQmolecules coexisting as different forms in aqueous solution. Absorption and resonance Raman spectroscopicmethods were used to examine 8-bromo-7-hydroxyquinoline protected acetate (BHQ-OAc) in acetonitrile(MeCN), H_2O/MeCN (60:40, v/v, pH 6-7), and NaOH-H_11??12) to obtain abetter characterization of the forms of the ground-state species of BHQ-OAc in aqueous solutions and toexamine their properties. The absorption spectra of BHQ-OAc in water show no absorption bands of thetautomeric species unlike the strong band at about 400 nm observed for the tautomeric form in 7-HQ aqueoussolution. The resonance Raman spectra in conjunction with Raman spectra predicted from density functionaltheory (DFT) calculations reveal the observation of a double Raman band system characteristic of the neutralform (the nominal C=C ring stretching, C-N stretching, and O-H bending modes at 1564 and 1607 cm-1)and a single Raman band diagnostic of the enol-deprotonated anionic form (the nominal C=C ring, C-N,and C-O~-stretching modes in the 1593 cm~(-1) region). These results suggest that neutral form of BHQ-OAcis the major species in neutral aqueous solution. There is a modest increase in the amount of the anionic formand a big decrease in the amount of the tautomeric form of the molecules for BHQ-OAc compared to 7-HQin neutral aqueous solution. The presence of the 8-bromo group and/or competitive hydrogen bonding thathinder the formation and transfer process of a BHQ-OAc-water cyclic complex may be responsible for thislarge substituent effect.
机译：8-溴-7-羟基喹啉基（BHQ）是7-羟基喹啉（7-HQ）和BHQ分子以水溶液形式共存的衍生物。吸收和共振拉曼光谱法用于检测在乙腈（MeCN），H_2O / MeCN（60:40，v / v，pH 6-7）和NaOH- H_11→12）可以更好地表征水溶液中BHQ-OAc的基态物种的形式并检验其性能。 BHQ-OAc在水中的吸收光谱没有显示互变异构物质的吸收带，这与在7-HQ水溶液中观察到的互变异构形式在约400 nm处的强谱带不同。共振拉曼光谱与根据密度泛函理论（DFT）计算预测的拉曼光谱一起揭示了中性形式的双拉曼能谱系统特征的观察结果（标称C = C环拉伸，CN拉伸和OH弯曲模式分别位于1564和1607） cm-1）和单个拉曼带诊断的烯醇去质子化的阴离子形式（标称C = C环，CN和CO〜拉伸模式在1593 cm〜（-1）区域）。这些结果表明，BHQ-OAcis的中性形式是中性水溶液中的主要物种。与7-HQin中性水溶液相比，BHQ-OAc分子的阴离子形式的量适度增加，而互变异构形式的量则大幅减少。 8-溴基团和/或竞争性氢键的存在阻碍了BHQ-OAc-水环状络合物的形成和转移过程，可能是造成这种大取代基作用的原因。

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