The present letter reports unusual high fluorescence anisotropy of excited state intramolecular proton transfer (ESIPT) prone 2-(2′-hydroxyphenyl)benzoxazole (HBO) in water followed by its imidazole (HBI) and thiazole (HBT) analogues. The low fluorescence anisotropy of the acetate compound of HBO in water reveals the key role of the hydrogen bonded cage-like probe-water cluster for the findings in water. Formation of the aquated cluster is controlled possibly by the combined effect of the electronegativity and mesomeric effect of the heteroatom away from the ESIPT site. The work invites further explorations, preferably from computational perspective, for a proper explanation.

本信报道了水中兴奋态分子内质子转移（ESIPT）易生的2-（2'-羟基苯基）苯并恶唑（HBO）及其随后的咪唑（HBI）和噻唑（HBT）类似物的异常高荧光各向异性。HBO乙酸盐化合物在水中的低荧光各向异性揭示了氢键笼状探针-水簇对于水中发现的关键作用。水合簇的形成可能受电负性和杂原子远离ESIPT位点的介观效应的共同作用控制。这项工作最好是从计算角度出发，进行进一步的探索，以寻求适当的解释。