title: Paraquat substituent effect on complexation with a dibenzo-24-crown-8-based cryptand.
abstract: Dibenzo-24-crown-8-based cryptand 4 forms 1:1 inclusion complexes with three paraquat derivatives, P1, P2, and P3, as demonstrated by proton NMR spectroscopy and X-ray analysis. However, it was found that methyl-substituted paraquat derivatives, P2 and P3, can bind cryptand 4 more strongly than non-methyl-substituted paraquat derivative P1. The association constants (Ka) were determined in acetone by using a UV-vis titration method to be 5.0 x 10(3) M(-1) for 4.P1, 1.0 x 10(5) M(-1) for 4.P2, and 1.2 x 10(5) M(-1) for 4.P3, respectively. In the solid state, 4.P2 and 4.P3 have similar T-type inclusion complexation conformations, which are very different from the pseudorotaxane-type complexation conformation of 4.P1. Theoretical calculations were done to explain these experimental results.
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou, PR China.
authors.forename: Jinqiang
authors.initials: J
authors.lastname: Zhang
authors.forename: Feihe
authors.initials: F
authors.lastname: Huang
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.forename: Harry W
authors.initials: HW
authors.lastname: Gibson
authors.forename: Peter
authors.initials: P
authors.lastname: Gantzel
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold