Theoretical study on intermolecular interactions of 2,4-dinitroimidazole with methanol

Nine optimized conformers of 2,4-dinitroimidazole with methanol have been obtained at B3LYP/6-31++G(2d,p) level. The intermolecular interaction energies are predicted by using MP2/6-31++G(2d,p), B3LYP/6-31++G(2d,p) and B3LYP/aug-cc-pVTZ methods with basis set superposition error (BSSE) and zero-point energy (ZPE) correction, and natural bonding analysis has also been carried out. The four main types of hydrogen bonds, which are N-H...O, C-H...O, O-H...O and O-H...pi, are investigated. The results indicate that only two of the conformers are the stable ones with the intermolecular interaction energies of 42.39 and 26.27 kJ/mol at B3LYP/aug-cc-pVTZ level, respectively. For these two conformers, the N-H...O or C-H...O hydrogen bonding interaction is dominant and the hydroxyl oxygen offers lone pairs to the contacting u(N-H)* or T(C-H)* antibond orbital of 2,4-dinitroimidazole and electrons transfer from methanol to 2,4-dinitroimidazole, while for the other conformers, the O-H...O or O-H...pi hydrogen bonding interaction is dominant and the nitro oxygen offers p electrons or imidazole ring offers part of the pi electrons to the sigma(O-H)* antibond orbital and the electrons transfer reversely. Intermolecular binding interaction between the nitro oxygen and hydroxylic hydrogen is relatively weak, as is in accordance with the literature. (c) 2006 Elsevier B.V. All rights reserved.