Theoretical and experimental studies on selected 1,3-diazolium salts

An analysis of the molecular structures of the benzyl and adamantyl derivatives of 1,3-diazolium salts in solid state was carried out based on the detailed interpretation of their vibrational spectra. The description of IR and Raman spectra was supported by DFT (B3LYP) calculations of the unsubstituted and substituted imidazolium cations as models. These results allowed finding markers bands originated mainly from the stretching, rocking and wagging vibrations of the C-2-H bond. Additionally, calculations of the heteroaromaticity (HOMA index) showed that cation formation causes dearomaticity of the imidazole ring. However, the substitution of the cationic species by the benzyl and adamantyl groups increases aromatic nature of the heterocyclic moiety. Moreover, the electron distribution performed using the GAPT method indicated the positive charge delocalization in the ring. [GRAPHICS] (C) 2006 Elsevier B.V. All rights reserved.