Supramolecular assembly and host–guest interaction of crown ether with inorganic acid and organic amine containing carboxyl groups

Abstract

Four rotator–stator assembly complexes: benzoic-4-methylammonium-tetrafluoroborate-15-crown-5 ([C₈H₁₀NO₂-(15-crown-5)]⁺[BF₄]⁻, 1); benzoic-4-methylammonium-perchlorate-15-crown-5 ([C₈H₁₀NO₂-(15-crown-5)]⁺[ClO₄]⁻, 2); benzoic-4-methylammonium-tetrafluoroborate-18-crown-6 ([C₈H₁₀NO₂-(18-crown-6)]⁺[BF₄]⁻, 3); benzoic-m-ammonium-tetrafluoroborate-18-crown-6 ([C₇H₈NO₂-(18-crown-6)]⁺[BF₄]⁻, 4), for the investigation of the supramolecular assembly and host–guest interaction of crown ethers, have been synthesized and characterized. The results revealed that the variation of crown ethers, the substituent position of carboxyl group, as well as the different kinds of inorganic anions all can lead to quite another geometry and directionality of both the anilinium rotors and crown ether stators, which lead to entirely different supramolecular architectures. It is interesting that the optimal distances from the mean O-plane where found for the 18-crown-6 macrocycle with the ammonium cation, and the conformation of the macrocycle was badly affected in complexes with shorter or longer distances. We also studied the Raman spectroscopy of the five complexes, which give further inspection of the intermolecular interactions.