α-环糊精与4-(N,N-二甲氨基)苯甲酸酯包合作用的光谱学研究

Spectroscopic studies on the inclusion of α-cyclodextrin with 4-(N,N-dimethylamino) benzoate

用分子光谱法研究了α-环糊精(α-CD)与4-(N,N-二甲氨基)苯甲酸(DMABA)、4-(N,N-二甲氨基)苯甲酸乙酯(EDMAB)、4-(N,N-二甲氨基)苯甲酸异戊酯(IADMAB)和4-(N,N-二甲氨基)苯甲酸异辛酯(EHDMAB)分子间的包合作用.比较了α-CD与DMABA、EDMAB、IADMAB和EHDMAB所形成包合物的组成和结合位点,根据主-客体分子的大小和结构探讨了相应的包合机理,具有较短碳链的EDMAB和IADMAB分子是4-(N,N-二甲氨基)端优先进入-αCD空腔,而对带有疏水性长碳链的EHDMAB分子是柔性的异辛基端优先进入α-CD空腔,因此,-αCD与EDMAB、IADMAB和EHDMAB形成了不同类型的1∶1型主-客体包合物.随着溶液中α-CD浓度的增大,4-(N,N-二甲氨基)苯甲酸酯分子未被包合部分可再结合一个α-CD形成2∶1型的主-客体包合物.

The inclusion of DMABA, EDMAB, IADMAB and EHDMAB in the cavity of α-CD is examined by means of molecular spectra. The stoichiometry and binding sites of α-CD to DMABA, EDMAB, IADMAB and EHDMAB are compared. The mechanism of inclusion is discussed on the basis of molecular structures and sizes. The 4-（N, N-dimethylamino） group is preferentially included inside the cavity of α-CD in the case of EDMAB and IADMAB with a shorter hydrocarbon chain. On the contrary, the flexible hydrophobic isooctyl chain of EHDMAB preferentially penetrates into the cavity of α-CD and the 4-（N,N-dimethylamino） group protrudes outside the cavity. Thus α-CD forms different types of 1：1 host-guest inclusion complexes with EDMAB, IADMAB and EHDMAB. With increasing concentration of α-CD, another α-CD is capable of incorporating the other part of EDMAB, IADMAB and EHDMAB whose opposite end is already located inside the cavity of α-CD. The 2：1 host-guest inclusion complexes are formed in aqueous solution.