双核Salen锌配合物对含氮小分子的分子识别研究

合成并表征了由一定长度烷氧链桥连的新型双核SalenZn配合物简记为C₁₀-(SalenZn)₂],用紫外-可见光谱滴定方法测定了主体C₁₀-(SalenZn)₂与单齿客体咪唑(Im)、吡啶(Py)、双齿客体DABCO(1,4-重氮双环2.2.2]辛烷)及吡嗪(Pyrazine)等4种含氮客体间的轴向配位反应的配位数及缔合常数.结果表明,双核主体与咪唑、吡啶和吡嗪的配位数均为2,与DABCO的配位数为1;各主客体体系的缔合常数按K0(Im)>K0(DABCO)>K0(Pyrazine)>K0(Py)顺序递减.各主客体缔合反应的热力学参数Δ_rH0_m,Δ_rS0_m和Δ_rG0_m结果表明,此类识别过程均为放热和熵减少的过程.采用¹HNMR方法和分子动力学构象搜索方法对主体C₁₀-(SalenZn)₂与双齿客体DABCO间的分子识别行为及产物构型作了合理解释.通过量子化学计算进一步解释了主客体识别过程中光谱性质的变化.

Molecular Recognition of Dinuclear Salen Zinc Complex for Small Molecules with Nitrogen

A novel dinuclear Salen zinc complex was synthesized and characterized. The coordination number and association constants of axial coordination reaction of complex C₁₀-(Salen Zn)₂ towards imidazole, pyridine, DABCO and Pyrazine were measured by means of spectra technique. The coordination number for Im, Py and pyrazine were all 2, but for DABCO was only 1. The association constants of host-guest system decreased in the order of K0(Im)>K0(DABCO)>K0(Pyrazine)> K0(Py). The thermodynamic parameters Δ_rH_m0, Δ_rS_m0 and Δ_rG_m0 were determined. The results showed that recognition process was exothermic and entropy decrease. In addition, the studies by means of ¹H NMR and the conformations with minimal energy of the host-guest were sought by simulated annealing method, which gave the reasonable explanation for the conformation of the host C₁₀-(Salen Zn)₂ and DABCO forming complex, the spectral changes of host-guest systems were explained by quantum chemical calculations.