The importance of C-H......N, C-H......π and π......π interactions in the crystal packing of the isomeric N1,N4- bis((pyridine-n-yl)methylene)-cyclohexane-1,4-diamines, n = 2, 3 and 4

Abstract

The molecular structures of the isomeric N1,N 4-bis((pyridine-n-yl)methylene)-cyclohexane-1,4-diamines, where n = 2 (1), 3 (2) and 4 (3), show the same effective conformation, in particular between the n-pyridine rings and the bridging cyclohexane rings. Theoretical structures of 1-3 are more symmetric and confirm that the pyridine residues are orthogonal to the plane through the four methylene groups of the bridging cyclohexyl groups. Crystal packing in 1-3 is dominated by C-H......N pyridine interactions. In 1, these interactions lead to linear chains and, along with π......π contacts, give rise to a layer structure. In 2, the C-H......Npyridine interactions extend in three dimensions and are complemented by C-H......N imine and C-H......π contacts. Finally, in 3, the C-H......Npyridine interactions lead to layers that are connected by C-H......π interactions to give a 3D network. It appears that in the structures of 1-3, the relative disposition of the pyridine and imine groups allows for the participation of the former in intermolecular interactions owing to their accessibility compared with the latter. © The Royal Society of Chemistry.