Improving the stability of 2-phenyl-1,3-dimethyl imidazolium cations under alkaline conditions through various substitution strategies

The effects of various substituents at different substitution positions on the stability of imidazolium cations were investigated by studying the degradation reactions of several substituted 2-phenyl-1,3-dimethyl imidazolium cations (PDMIm⁺). The results of density functional theory calculations revealed that the stability of the imidazolium cation could be significantly enhanced by substitutions near the C2 position. These substitution positions included the ortho positions of the phenyl group and the N1/N3 and C4/C5 positions on the imidazole ring of PDMIm⁺. Moreover, the ethyl group was the most effective substituent among the ones discussed. The calculations also revealed that double alkyl substituents at ortho positions could more effectively improve the stability of imidazolium cations in the degradation reactions.