jo800890x_si_002.cif (54.4 kB)

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

Download (108.8 kB)
posted on 01.08.2008 by Chunlin He, Zuming Shi, Qizhong Zhou, Shijun Li, Ning Li, Feihe Huang
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).