EXCITED-STATE PROTON-TRANSFER OF PROTONATED 1-AMINOPYRENE COMPLEXED WITH BETA-CYCLODEXTRIN
EXCITED-STATE PROTON-TRANSFER OF PROTONATED 1-AMINOPYRENE COMPLEXED WITH BETA-CYCLODEXTRIN
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DOI：
10.1021/j100196a011
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发表时间：
1992-08-20
影响因子：
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通讯作者：
FLEMING, GR
中科院分区：
文献类型：
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作者：
HANSEN, JE;PINES, E;FLEMING, GR
用时间分辨光谱法研究了1-氨基芘和α-萘酚与环糊精包合物的激发态质子转移。我们发现，动力学研究是更敏感的络合比稳态光谱测量。我们的数据表明，两个不同的1-氨基芘结合β-环糊精的结合方向。与纯水相比，质子转移速率增加2-3倍，包合络合物类似于接近75%体积醇组成的水-乙醇混合物。氘化增强的解离速率的一个因素的3.5，在80%（体积）的乙醇-水混合物和离子的复合物与β-环糊精。在α-萘酚的情况下，包合络合物中的质子转移速率显著减慢，并且具有80体积%乙醇-水混合物的预期速率。我们认为，β-环糊精的空腔边缘附近的水被修改的广泛的网络的OH基团以这样的方式，以增加其碱性。在酶系统中也可能发生类似的效应。
Excited-state proton transfer in inclusion complexes of 1-aminopyrene and alpha-naphthol with cyclodextrins was studied by time-resolved spectroscopy. We find that the kinetic studies are much more sensitive to the complexation than are steady-state spectroscopic measurements. Our data suggest two distinct binding orientations for 1-aminopyrene bound to beta-cyclodextrin. The rate of proton transfer is increased by a factor of 2-3 compared to pure water with the inclusion complex resembling a water-ethanol mixture near the 75% by volume alcohol composition. Deuteration enhances the dissociation rate by a factor of 3.5 in both 80% (by volume) ethanol water mixtures and ion the complex with beta-cyclodextrin. In the case of alpha-naphthol the rate of proton transfer slows considerably in the inclusion complex and has the rate expected for an 80% by volume ethanol-water mixture. We suggest that the water near the cavity rim of beta-cyclodextrin is modified by the extensive network of OH groups in such a way as to increase its basicity. Similar effects may occur in enzymic systems.