盐酸巴马汀与葫芦[7]脲的相互作用及荧光增敏机理探讨

Study on the Interaction Between Palmatine Hydrochloride and Cucurbit[7]uril and the Mechanism of Fluorescence Enhancement

采用荧光光谱法和核磁共振技术(1H NMR)研究了葫芦[7]脲(CB[7])与盐酸巴马汀(PAL)之间的超分子作用,无荧光的CB[7]可以与弱荧光的PAL相互作用形成1∶1的主客体包结配合物,同时产生强大的荧光发射,其包结稳定常数K=1.18×105 L.mol-1。热力学常数△G、△H和△S计算结果说明反应是焓变驱动。分子模型通过高斯密度泛函理论计算。在能量最小化结构中,PAL分子中含甲氧基的异喹啉部分进入CB[7]的疏水空腔,形成内包结物。苯环和异喹啉环的二面角从23.37°变为-8.09°。从而确定了PAL在CB[7]存在下产生强大的荧光发射的主要因素。此外,1H NMR研究和分子模型计算推导出了主客体之间相互作用的机理,确定了包结配合物的形成过程。

The supramolecular interaction between palmatine hydrochloride（PAL） and cucurbit[7] uril （CB[7]） was studied by fluorescence spectrometry and 1H NMR. CB[7] reacts with PAL to form a stable 1＂1 host-guest complex,and produces a strong fluorescence emission. The association constant（K = 1.18）〈 10a L.mol t） was calculated by applying a deduced equation. From the temperature dependence of the equilibrium constants, thermodynamics parameters H and S values were obtained, indicating an enthalpic driving force for complexation. Molecular modeling calculations were optimized at the B3LYP/ 6-31G（d） level of density functional theory using the Gaussian 03 program. In the energy-minimized structure, the methoxy-isoquinoline moiety is embedded in CB[-7], and the heterocyclic nitrogen is located in the vicinity of a carbonyl-laced portal. Two hydrogen bonds are formed between the heterocyclic nitrogen and carbonyl oxygen of CB[7]. The dihedral angle between the isoquinoline and the substituted benzene ring varies from 23.37° to --8.09°. The main factors of strong fluorescence emission from PAL- CB[-7] complex have been identified. In addition, the mechanism of host-guest interaction has been derived by 1H NMR and molecular modeling calculation,and the formation steps of inclusion complexes has also been identified.