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乙烯、苯与Li+、Na+、K+形成的阳离子-π复合物结构的理论研究 总被引:1,自引:0,他引:1
系统地研究了乙烯、苯与Li+、Na+、K+形成的阳离子-π复合物的结构.发现在乙烯与Li+、Na+、K+阳离子形成的复合物中,乙烯分子的C-H键与形成复合物前相比伸长了,然而,在苯的阳离子-π复合物中,苯分子的C-H键却出乎意料地变短了(特别是在锂离子-π复合物中).这种现象可能与最近由Hobza等人发现的蓝移氢键现象有相同的机理. 相似文献
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精确计算化学键解离能的ONIOM-G3B3方法及其在抗氧化剂研究中的应用 总被引:1,自引:0,他引:1
通过对179个有机化合物C—H, N—H, O—H键离解能的理论计算, 系统评估了高精度组合从头算方法(ONIOM-G3B3)和密度泛函理论方法(B3LYP)在预测键离解能上的可靠性. 研究发现ONIOM-G3B3方法可以准确预测各类有机化合物的键解离能, 精度达到5.9 kJ/mol. 运用ONIOM-G3B3方法成功预测了两类重要的天然抗氧化剂维生素E族和茶多酚族的键解离能, 并进一步讨论了抗氧化活性、自由基清除机理及其构效关系. 相似文献
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合成系列含缩醛的双链正离子类脂分子 ,并用荧光光谱研究其与牛血清蛋白 (BSA)的相互作用 .通过荧光的变化 ,解释蛋白质构象的变化 .在低类脂浓度时 ,少量类脂分子束缚在牛血清蛋白周围 ,荧光有很大幅度的淬灭 ,蛋白质本身肽链被解开 ,与此同时最大发射波长从 (3 44± 1)nm蓝移到 (3 3 1± 1)nm .由于疏水相互作用 ,更多类脂分子不断地聚集在蛋白质周围 ,牛血清蛋白中的两个色氨酸残基被完全地包裹在类脂分子形成的双分子膜中 ,荧光强度不断增加直到恒定不变 相似文献
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CBS-Q and G3 methods were used to generate a large number of reliable Si--H, P---H and S--H bond dissociation energies (BDEs) for the first time. It was found that the Si--H BDE displayed dramatically different substituent effects compared with the C--H BDE. On the other hand, the P---H and S--H BDE exhibited patterns of substituent effects similar to those of the N--H and O--H BDE. Further analysis indicated that increasing the positive charge on Si of XSiH3 would strengthen the Si--H bond whereas increasing the positive charge on P and S of XPH2 and XSH would weaken the P---H and S--H bonds. Meanwhile, increasing the positive charge on Si of XSiH2^+ stabilized the silyl radical whereas increasing the positive charge on P and S in XPH" and XS* destabilized P- and S-centered radicals. These behaviors could be reasonalized by the fact that Si is less electronegative than H while P and S are not. Finally, it was demonstrated that the spin-delocalization effect was valid for the Si-, P- and S-centered radicals. 相似文献
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A series of fluorescent chemosensors 1-3 were synthesized to detect transition metal ions. At the room temperature, fluorescence intensities of these chemosensors in acetonitrile without transition metal ions were found to be very weak, due to the process of the e±cient intramolecular photoinduced electron transfer (PET). However, after addition of the transition metal ions, the chemosensor 1-3 exhibits obvious fluorescence enhancement. Moreover, the intensity of the fluorescence emission of chemosensors increases significantly in the presence of Zn2+ and Cd2+. The fluorescent chemosensors with different polyamine as receptors show diverse a±nity abilities to the transition metal ions and signal the receptor-metal ion interaction by the intensity change of fluorescence emission. 相似文献