Complexation of naphthylethanols with β-cyclodextrin
Complexation of naphthylethanols with β-cyclodextrin
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DOI：
10.1021/jp9803844
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发表时间：
1998-07-09
影响因子：
2.9
通讯作者：
Bohne, C
中科院分区：
文献类型：
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作者：
Barros, TC;Stefaniak, K;Bohne, C
采用多种光谱技术研究了1-NpOH和2-NpOH与β-环糊精（β-CD）的络合行为。在1-NpOH的情况下，仅与β-CD形成化学计量比为1：1的复合物，平衡常数小于β-CD和2-NpOH之间1：1复合物的平衡常数。在β-CD存在下，观察到含有高浓度2-NpOH的溶液的准分子发射。这种激基缔合物发射归因于具有2：2 β-CD/2-NpOH化学计量的复合物。此外，H-1 NMR数据表明2-NpOH轴向并入β-CD空腔。仅在2-NpOH的情况下，在β-CD存在下观察到对应于芳族质子的信号变宽。这种增宽归因于2：2络合物的形成。用三重态猝灭法研究了NpOH络合动力学。1-NpOH和2-NpOH的1：1复合物的进入速率常数分别为（4.7 +/- 1.9）x 10（8）M-1 s（-1）和（2.9 +/- 1.6）x 10（8）M-1 s（-1），而两种化合物的退出速率常数分别为（4.8 +/- 1.8）x 10（5）s（-1）和（1.8 +/- 0.7）x 10（5）s（-1）。在2-NpOH的情况下，我们首次能够估计β-CD 2：2复合物解离的速率常数（（0.2-2.5）x 10（3）s（-1）），表明包含一种以上环糊精的复合物的动力学明显慢于1：1复合物的动力学。
The complexation behavior of 1-naphthyl-1-ethanol (1-NpOH) and 2-naphthyl-1-ethanol (2-NpOH) with beta-cyclodextrin (beta-CD) was studied by employing several spectroscopic techniques. In the case of 1-NpOH, only a complex with 1:1 stoichiometry is formed with beta-CD, which. has an equilibrium constant that is smaller than that observed for the 1:1 complex between beta-CD and 2-NpOH. Excimer emission was observed in the presence of beta-CD for solutions containing high 2-NpOH concentrations. This excimer emission was ascribed to a complex with 2:2 beta-CD/2-NpOH stoichiometry. In addition, H-1 NMR data suggest that 2-NpOH is axially incorporated into the beta-CD cavity. Only in the case of 2-NpOH was a broadening of the signals corresponding to the aromatic protons observed in the presence of beta-CD. This broadening was attributed to the formation of the 2:2 complex. The dynamics of NpOH complexation was investigated by using the quenching methodology for triplet states. The entry rate constants for the 1:1 complex of 1-NpOH and 2-NpOH are (4.7 +/- 1.9) x 10(8) M-1 s(-1) and (2.9 +/- 1.6) x 10(8) M-1 s(-1), respectively, whereas the exit rate constants for the two compounds are (4.8 +/- 1.8) x 10(5) s(-1) and (1.8 +/- 0.7) x 10(5) s(-1). In the case of 2-NpOH, we were able for the first time to estimate the rate constant for the dissociation of a beta-CD 2:2 complex ((0.2-2.5) x 10(3) s(-1)), showing that the dynamics for complexes including more than one cyclodextrin are remarkably slower than the dynamics observed for 1:1 complexes.