The structures and stability of hydrogen bond (HB) complexes of hydrogen fluorides (HF)(n) (n = 1-6) clusters with imidazole have been investigated by ab initio molecular orbital and density functional theory (DFT) methods. The natural bond orbital (NBO), frontier molecular orbital (FMO), and nucleus-independent chemical shifts (NICS) analyses have revealed the aromaticity of the imidazole or protonation imidazole ring in these complexes. (c) 2006 Elsevier B.V. All rights reserved.