Role of intermolecular interactions in formation of mono- and diaminopyridine crystals: study from the energetic viewpoint

The regularities of crystal structure organization in a series of mono- and diaminopyridines possessing biological activities were studied using an approach based on comparison of interaction energies between molecules calculated by ab initio quantum chemical method. The presence of the pyridine nitrogen atom causes the formation of N–H…Npyr hydrogen bond which is the strongest in all the studied structures. Being amphiphilic in hydrogen bond formation, the amino group possesses acceptor properties only in meta-position to the pyridine nitrogen atom in mono-aminopyridines. The presence of the two amino groups results in increasing of acceptor properties of both ones. The N–H…Nlp hydrogen bonds bind primary BSM (basic structural motif) in the structures of 2,5-diaminopyridine, 2,4-diaminopyridine and 3,4-diamonpyridine and form the primary BSM alongside with N–H…Npyr hydrogen bond in the structure of 2,3-diaminopyridine. The helical primary basic structural motif and double helical secondary basic structural motif in the 2,3-diaminopyridine crystal structure are very similar to the DNA helix and double helix.