A Supramolecular Investigation on the Interactions between Ethyl terminated Bis–viologen Derivatives with Sulfonato Calix[4]arenes

Abstract

AbstractHerein, we report the synthesis and guest‐host complexation between isomeric xylylene interconnected ethyl terminated bis‐viologens (EDV) with p‐sulfonatocalix[4]arene (SC4 A). Guest‐host interactions between EDV and SC4 A were monitored by CV (cyclic voltammetry), 1H and DOSY (Diffusion Ordered Spectroscopy) NMR titrations. CV titrations showed a partial inclusion complex formation between EDV and SC4 A which is further confirmed by 1H NMR and DOSY titrations. It is evident from 1H NMR titrations that all the three isomers of EDV forms a stable inclusion complex with SC4 A where SC4 A caps the terminal. o‐ and m‐ isomers of EDV interacts differently than their corresponding p‐isomer. 1H NMR titration reveals that o‐ and m‐xylylene units are incorporated into the SC4 A cavity whereas p‐xylylene unit is only partially included into the cavity during the interaction. Further, it is observed that the ethyl terminated viologen adopts axial orientation in concordance with previous reports. DOSY measurements further confirmed the formation of inclusion complex between the bis‐viologen and SC4 A and indicated the formation of aggregates at higher concentrations of SC4 A. Results clearly indicate that the bis‐viologens possess multiple binding sites for the multivalent SC4 A host and based on the concentration of SC4 A, several types of interactions exists between the two predicting a complex binding model.