Proton conducting system (ImH 2 ) 2 SeO 4 ·2H 2 O investigated with vibrational spectroscopy.

Imidazolium selenate dihydrate (ImH2 )2 SeO4 ·2H2 O crystals have been investigated using Raman and IR spectroscopy. Experimental data were supported by the quantum-chemical calculations (DFT), Hirshfield surfaces and fingerprint plots analysis, and Bader theory calculations. The imidazolium selenate dihydrate crystal exhibits high proton conductivity of the order of ~10-1 S/m at T=333K. The spectra of this compound are dominated by bands related to the lattice modes, the internal vibrations of the protonated imidazole cation, selenate anion, water molecules, and hydrogen bonds network. For the imidazolium selenate dihydrate crystal, the formal classification of the fundamental modes has been carried out.