Syntheses of cis- and trans-Dibenzo-30-Crown-10 Derivatives via Regioselective Routes and Their Complexations with Paraquat and Diquat

cis-Dibenzo-30-crown-10 (cis-DB30C10) diester and trans-dibenzo-30-crown-10 (trans-DB30C10) diester were synthesized regioselectively with reasonable yields. These two isomers were further reduced to cis-dibenzo-30-crown-10 diol (1) and trans-DB30C10 diol (2), respectively. The complexations of cis- and trans-DB30C10 diols with paraquat (3) and diquat (4) were investigated by 1H NMR, mass spectrometry, UV−vis spectroscopy, and single-crystal X-ray analysis. The reversible control of complexations of 1·3 and 2·3 by adding small molecules (KPF6 and dibenzo-18-crown-6) was demonstrated by 1H NMR. The addition of 2 molar equiv of KPF6 is enough to dissociate 2·3 and 1·3 completely while the subsequent addition of 2 molar equiv of DB18C6 allows the two complexes to reform. However, 2 molar equiv of KPF6 cannot dissociate 1·4 and 2·4 completely. Because the DB30C10 cavity has a better geometry fit with paraquat 3 than with diquat 4, 4-based complexes have much higher association constants than the corresponding 3-based complexes. In the crystal structure of 1·4, the two hydroxymethyl groups of the crown ether 1 were joined by a “water bridge” to form a “supramolecular cryptand” while this kind of supramolecular cryptand structure was not observed in the crystal structure of 2·4. This is a possible reason for the increase in association constant from 2·4 (3.3 × 104 M−1) to 1·4 (5.0 × 104 M−1).

cis-二苯并-30-冠-10 (cis-DB30C10) 酯和trans-二苯并-30-冠-10 (trans-DB30C10) 酯通过区域选择性合成，产率合理。这两种异构体进一步被还原为cis-二苯并-30-冠-10 二醇（1）和trans-DB30C10 二醇（2）。通过1H NMR、质谱分析、紫外-可见光谱和单晶X射线分析，研究了cis-和trans-DB30C10 二醇与对氯苯基二甲基铵（3）和二氯苯基二甲基铵（4）的络合作用。通过1H NMR证明了通过添加小分子（KPF6和二苯并-18-冠-6）可以可逆地控制1·3和2·3的络合作用。添加2摩尔当量的KPF6足以完全解离2·3和1·3，而随后的添加2摩尔当量的DB18C6则允许这两个络合物重新形成。然而，2摩尔当量的KPF6不能完全解离1·4和2·4。由于DB30C10腔体与对氯苯基二甲基铵3的几何适配性优于与二氯苯基二甲基铵4，基于4的络合物比相应的基于3的络合物具有更高的结合常数。在1·4的晶体结构中，冠醚1的两个羟甲基通过“水桥”连接形成一个“超分子隐囊”，而这类超分子隐囊结构在2·4的晶体结构中并未观察到。这可能是2·4（结合常数为3.3×10^4 M−1）至1·4（结合常数为5.0×10^4 M−1）结合常数增加的可能原因。