Influence of the angle between two crown ether moieties on supramolecular copolymerization of bis(crown ether)s and bisparaquat homoditopic monomers

Abstract

Bis(crown ether) homoditopic monomers containing two bis(p-phenylene)-34-crown-10 moieties with different angles (180 for monomer 3, 120 for monomer 4, and 60 for monomer 5) and a complementary bisparaquat homoditopic monomer (7) were designed and synthesized. The three bis(crown ether) monomers could organize into linear supramolecular polymers in concentrated solutions in CHCl 3 /CH 3 CN with the bisparaquat monomer 7, as demonstrated by 1 H NMR and viscosity studies. The pseudorotaxanes or supramolecular polymers formed from 3+7 and 4+7 had larger values of K a , p, n, slope 1, and slope 2 than those of 5+7. This result was attributed to the greater steric hindrance of compound 5 than that of 3 and 4, which resulted in less effective formation of linear supramolecular polymers from 5 with compound 7 than those from compounds 3 and 4 with compound 7, as also demonstrated by UV-vis method. bis(crown ether), bisparaquat homoditopic monomers, angle, supramolecular copolymerization

Supramolecular AA−BB-Type Linear Polymers with Relatively High Molecular Weights via the Self-Assembly of Bis(m-phenylene)-32-Crown-10 Cryptands and a Bisparaquat Derivative

“…Further direct physical evidence for the formation of a large, supramolecular, noncovalent polymer was obtained from a viscosity study. A double-logarithmic plot of specific viscosity versus the initial concentrations of equimolar solutions of 3 and 5 in 1:1 (v/v) chloroform/acetonitrile (Figure a) yielded a curve with slope of 1.02 at low concentrations, indicating the existence of cyclic species, as with crown ether-based systems . At high concentrations, the curve had a slope of 2.64, indicating the formation of linear supramolecular polymers 1 of increasing size.…”

“…Because of architectural differences from traditional covalent polymers, supramolecular polymers, in which noncovalent, mechanically interlocked structures play an important role, are expected to have unique properties and potential applications . In the past decade, supramolecular polymers have been widely studied, and a large variety is known. − Among them, crown ether-based pseudorotaxane-type supramolecular polymers are very attractive and have been used to prepare various architectures, such as linear, branched, star-shaped, and dendronized . However, in order to prepare large supramolecular polymers, monomers with high association constants are required. ,, Cryptands have proved to be much better hosts for paraquat derivatives than the corresponding simple crown ethers; for example, the association constant for hydroxyl-functionalized cryptand 6 and dimethyl paraquat ( K a = 6.3 × 10 3 M −1 in acetone at 22 °C) is ∼13-fold higher than that between bis( m -phenylene)-32-crown-10 (BMP32C10) and dimethyl paraquat .…”