Molecular structure of 1,3-bis(carboxymethyl)imidazolium bromide and its betaine form in crystal

1,3-Bis(carboxymethyl)imidazolium bromide [(C7H9N2O4)+Br−] has been studied by X-ray diffraction, FT-IR and Raman spectroscopy. In the crystalline state, two 1,3-bis(carboxymethyl)imidazolium bromide molecules are hydrogen-bonded via carboxylic groups forming a symmetric dimer. Within the dimer structure the other carboxylic groups are hydrogen bonded to Br− anions. Both types of intermolecular hydrogen bonds are the relatively weak. In the solid state the Br− anions interact with both ring and with the aliphatic C–H protons. Furthermore, the betaine derivative form in the solid state a chain via strong homoconjugated (O–H···O)− hydrogen bonds. The nature of these hydrogen bonds is well reflected by the proton vibrations in the FT-IR spectra of the compounds studied. As follows from the ESI-MS results the compounds studied are not able to complex mono- and di-valent metal cations in the gas phase.