Effect of heteropoly acids on structure, electrochemical behavior, acidic properties and catalytic activity of zwitterionic-type ionic liquid

Abstract

Zwitterionic-type ionic liquid (CDIPS) was prepared by the reaction of 1,1′-carbonyldiimidazole (CDI) with 1,3-propane sultone (PS). 1H NMR, XRD, FT-IR and CHNS confirm that 1,3-propane sultone was attached to two N atoms. Inorganic–organic hybrids based on SO3H-functionalized cations and Keggin-type heteropoly acids as anions (H3PW12O40, H3PMo12O40, and H4SiW12O40; HPAs) were prepared and characterized. The electronic properties of the center-metal ions in hybrid salts and their electrochemical behavior were studied through UV and cyclic voltammetry (CV) respectively. Catalytic activities of the organic-inorganic HPA salts were studied in the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]-xanthene-11-one derivatives. Relationship between catalytic activity and both of acidic strength and the number of acid sites of the catalysts was discussed and proved by potentiometric titration. The catalyst was readily recovered and reused for four runs. Moreover, the best catalyst was characterized more by FT-IR, XRD, SEM/EDX, ICP-OES, BJH and CHNS.