Hydrogen bonding in aromatic polyamine 2-guanidinobenzimidazole: Study based on density functional theory calculations

The role of inter- and intramolecular hydrogen bonding is very important for defining the reactivity of a great diversity of structures. In aromatic nucleophilic substitutions (SNAr) with amines in aprotic solvents, the attendance of hydrogen bond interactions (solute-solute and solute-solvent) has been proposed to understand kinetic results. In order to hold up recently reported experimental results on SNAr, in this paper we study structural and electronic properties of the aromatic polyamine 2-guanidinobenzimidazole, the aprotic polar solvent molecule dimethylsulphoxide and their interactions. Semi-empirical and ab-initio density functional theory calculations were performed to investigate, in particular, the possibility of hydrogen bond formation. It is found that 2-guanidinobenzimidazole presents intra- and intermolecular hydrogen bond formation leading to homo 2-GB and mixed solute-solvent dimers; being the latter energetically slightly more favorable than the former one.