手性不对称Salen Ni对咪唑类和二胺类客体的分子识别研究

用紫外-可见光谱滴定法研究了新型手性不对称Salen Ni主体(1和2)与咪唑类和二胺类客体的分子识别行为. 结果表明, 二胺类客体的缔合常数顺序为Kθ(乙二胺)>Kθ(丙二胺); 咪唑类客体的缔合常数顺序为Kθ(Im)>Kθ(N-MeIm)>Kθ(2-MeIm)>Kθ(2-Et-4-MeIm), 除主体2对2-乙基-4-甲基咪唑的配位数为1外, 其它体系的配位数均为2. 通过测定识别过程的热力学函数ΔrHθm和ΔrSθm发现, 反应为放热、熵减少过程; 利用圆二色光谱研究了识别过程中的主-客体结合能力的强弱; 用分子力学方法研究了主客体体系的最低能量构象, 并通过量化计算对实验事实做了进一步解释.

Studies on Molecular Recognition of Chiral Asymmetry Salen Ni to Guests Imidazole and Diamine Derivatives

By method of UV-Vis spectraophotometric titration molecular recognition behavior of novel chiral asymmetry Salen Ni complexes(Host 1 and Host 2) with imidazoles and diamines in CHCl3 were studied. The results showed that the association constants decreased in the orders of Kθ(ethane-1,2-diamine)＞Kθ(propane-1,2-diamine)(diamine derivatives) and Kθ(Im)＞Kθ(N-MeIm)＞Kθ(2-MeIm)＞Kθ(2-Et-4-MeIm)(imidazole derivatives). When Salen Ni(host 1) reacts with 2-Et-4-MeIm, the coordination number is 1. In other systems the coordination number is 2. The thermodynamic functions ΔrHθm, ΔrSθm were also measured. The results indicated the processes were exothermic and entropy decreasing. The CD spectra of host-guest system was studied and the results were consistent with those of thermodynamics. Moreover, the lowest energy configurations of host-guest system were obtained by simulated annealing, and quantum chemical calculation was performed based on the configuration to explain the experimental results.