1,10-(1-H-imidazol-5-yl)decanephosphonic acid: a new compound with basic and acidic sites to fabricate proton-conducting solid electrolytes

2-(tert-butyldimethylsilyl)-5-(10-bromodecyl)-1-(N,N-dimethylsulfamoyl)-imidazole and NaPO3 Et2 react at room temperature to yield the corresponding imidazole diethyl phosphonate, which when refluxed with concentrated HBr yields 1,10-(1-H-imidazol-5-yl)decanephosphonic acid hydrobromide (VI). Compound VI titrated with the required mole equivalents of NaOH yields 1,10-(1-H-imidazol-5-yl)decanephosphonic acid (VII) and 1,10-(1-H-imidazol-5-yl)decane (sodium)phosphonates (VIII). CP-MAS NMR (13C, 31P, and 15N) and IR spectroscopy indicate that only compound VII is likely to yield a polymeric structure where each phosphonic acid group is H bonded to the imidazole ring of the same molecule and to the imidazole ring of another molecule. For this reason, solid-state proton conductivity in VII is likely to be favored.