Synthesis and characterization of vinylimidazolium salts: Solution state study to realize the influence of different anions

Abstract

New vinylimidazolium salts, [9,10-bis{(N-vinylimidazolium)methyl}anthracene] bistetrafluoroborate (2) and [9,10-bis{(N-vinylimidazolium)methyl}anthracene] bishexafluorophosphate (3) have been prepared by the N alkylation of 9,10-bis(chloromethyl)anthracene with 1-vinylimidazole in 1,4-dioxane at 70°C followed by the anion exchange reaction between [9,10-bis{(N-vinylimidazolium)methyl}anthracene] dichloride (1) and ammonium salt of tetrafluoroborate (for 2) or hexafluorophosphate (for 3). The interaction of tribromide anion with 1–3 has been studied with the help of 1H NMR and fluorescence spectra. Notably, the tribromide anion exhibits very strong fluorescent quenching effects towards 2 than 1 and 3. Similarly, 2 shows very strong fluorescent quenching effect in the presence of tribromide anion compare to bromide anion. Moreover the proton of imidazolium cation, NCHN in 2 undergoes considerable downfield shift in the presence of tribromide anion, while the vinyl group depicts strong upfield shift due to the possible interaction of tribromide with vinylimidazolium unit.