Hydrogen bonds and proton transfer in imidazole oligomers and (imidazole)2H(+) system: quantum-chemical calculations

Abstract

The semi-empirical PCILO method has been applied to study of hydrogen bonds and proton transfer in linear n-mers of imidazole (n = 3). The calculated hydrogen bond energy in the dimer is 30.64 kJ mol-1. In imidazole trimer interaction energy of the "second" hydrogen bond increased to 32.02 kJ mol-1. One-minimum functions only have been found by calculations of the proton potential functions in imidazole dimer and trimer for the equilibrium distances RN...N. For somewhat longer distances RN...N = 0.30 nm a second minimum was observed as shoulder. On the contrary, for the (imidazole)2H(+) system the proton potential curve has two minima for the equilibrium distance RN...N = 0.252 nm, the second minimum is more stable by 3.97 kJ mol-1.