Excited state intramolecular proton transfer and metal ion complexation of 2-(2′-hydroxyphenyl)benzazoles in aqueous solution
Excited state intramolecular proton transfer and metal ion complexation of 2-(2′-hydroxyphenyl)benzazoles in aqueous solution
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DOI：
10.1021/jp014634j
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发表时间：
2002-05-30
影响因子：
2.9
通讯作者：
Fahrni, CJ
中科院分区：
文献类型：
--
作者：
Henary, MM;Fahrni, CJ
用吸收光谱和稳态发射光谱研究了生理条件下一系列水溶性2-（2 ′-羟基苯基）苯并唑衍生物的激发态分子内质子转移（ESIPT）。在中性pH值下，在0.1 M的离子背景的存在下，这些衍生物的荧光性质与以前报道的非水溶剂中的数据相比，有很大的不同。ESIPT过程被破坏，可能是由于与周围水分子的分子间氢键结合以及反式旋转异构体的增加的稳定性，其不能经历ESIPT过程。苯并咪唑衍生物的发射光谱显著依赖于溶剂极性，如通过在甲醇、乙醇中用Zn（II）的滴定所揭示的，并且在生理条件下，通过金属配位抑制ESIPT显示出显著的波长偏移以及由13.7倍的大幅比率增加。滴定的苯并恶唑衍生物与Zn（II）产生了50倍的发射强度增加。该配体的荧光增强对Zn（II）是特异性的，logK为3.93（Kd = 117 μ M），适合作为生物环境中的荧光探针，以测量Zn（II）浓度在10 9 μ M至1 mM的范围内。
The excited-state intramolecular proton transfer (ESIPT) of a,series of water-soluble 2-(2'-hydroxyphenyl)benzazole derivatives has been studied under physiological conditions using absorbance and steady-state emission spectroscopy. At neutral pH in the presence of 0.1 M ionic background, the fluorescence properties of these derivatives differ substantially compared to previously reported data in nonaqueous solvents. The ESIPT process is disrupted, presumably due to intermolecular hydrogen bonding with surrounding water molecules combined with increased stabilization of the trans-rotamer, which cannot undergo the ESIPT process. The emission spectrum of the benzimidazole derivative depends significantly on the solvent polarity, as revealed by titrations with Zn(II) in methanol, ethanol, and under physiological conditions, Inhibition of ESIPT via metal coordination shows a significant wavelength shift together with a substantial ratio increase by a factor of 13.7. Titration of the benzoxazole derivative with Zn(II) yielded a 50-fold increased emission intensity. The fluorescence increase is specific for Zn(II), and with a logK of 3.93 (K-d = 117 muM) the ligand would be suitable as a fluorescence probe in a biological environment to gauge Zn(II) concentrations in the range from 10 9muM to 1 mM.