合成并表征了手性Salen配体1及其Zn配合物2.详细讨论了配体及配合物的电子光谱和圆二色光谱性质.用紫外-可见光谱滴定法测定了主体2与4种咪唑、5种吡啶客体轴向配位反应的平衡常数,研究了主体分子2的分子识别行为.实验结果表明:各种客体的缔合常数,咪唑类按K(Im)＞K(2-MeIm)＞K(SMIm)＞K(EMIm)顺序递减;吡啶类按K(Py)＞K(3-Py)＞K(3,5-Py)＞K(2,4-Py)＞K(2,4,6-Py)顺序递减.测定了识别过程的ΔrG m,ΔrH m,ΔrS m,发现该反应是放热、熵减小的过程.采用分子力学的方法考察了主客体的最低能量构象,并对该构象进行量子化学计算,从理论上对实验事实给予较好的解释.
Chiral salen 1 and chiral salen Zn complex 2 were synthesized and characterized. The electronic spectra and circular dichroism spectra properties were discussed. By method of UV-vis spectrophotometer technique, the equilibrium constants of axial coordination reaction were measured between complex 2 and series of imidazoles or pyridines. The molecular recognition of the host 2 was studied. The results show that the equilibrium constants decrease in the orders of K(Im)>K(2-MeIm)>K(SMIm)>K(EMIm) (imidazoles) and K(Py)>K(3-Py)> K(3,5-Py)>K(2,4-Py)>K(2,4,6-Py) (pyridines). The thermodynamic parameters Δ rG m, Δ rH m and Δ rS m of the recognition process were determined. It is found that the reaction is an exothermic process with entropy decreasing. In addition, the conformations with minimal energy of each host-guest molecular system were sought by molecular dynamics method. Quantum chemical calculations were performed on these conformations to explain the experimental data. A model of the recognition mechanism was constructed.
Acta Chimica Sinica