C-H•••O and C-H•••N interactions in three hexahydrocycloocta[b]pyridine-3-carbonitriles

The structures of three new pyridine derivatives, 2-methoxy-4-(4-methoxyphenyl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile, C20H22N2O2, (I), 2-ethoxy-4-(3-nitrophenyl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile, C20H21N3O3, (II), and 2-ethoxy-4-(4-methoxyphenyl)5,6,7,8,9,10-hexahydrocycloocta[b] pyridine-3-carbonitrile, C21H24N2O2, (III), differ in the nature of the substituents either at the 2-position of the central pyridine ring or on the pendent aryl ring. This simple change in the structure substantially alters the intermolecular interaction patterns. The substituted phenyl group adopts a synclinal geometry with respect to the plane of the pyridine ring in all three compounds. In (I), a C-H center dot center dot center dot N interaction results in a one-dimensional chain parallel to the b axis. In (II), there are two C-H center dot center dot center dot N(nitrile) interactions from different symmetry-related molecules, resulting in a two-dimensional network parallel to the bc plane. There is also a weak C-H center dot center dot center dot O interaction from the ethoxy group to an adjacent nitro O atom. The present work is an example of how the simple replacement of a substituent in the main molecular scaffold may transform the structure type, paving the way for a variety of supramolecular motifs and consequently altering the complexity of the intermolecular interaction patterns.