Crystal structures of 4-chloro­pyridine-2-carbo­nitrile and 6-chloro­pyridine-2-carbo­nitrile exhibit different inter­molecular π-stacking, C—H⋯Nnitrile and C—H⋯Npyridine inter­actions

The two title compounds are isomers of C6H3ClN2 containing a pyridine ring, a nitrile group, and a chloro substituent. The mol-ecules of each compound pack together in the solid state with offset face-to-face π-stacking, and inter-molecular C-H⋯Nnitrile and C-H⋯Npyridine inter-actions. 4-Chloro-pyridine-2-carbo-nitrile, (I), exhibits pairwise centrosymmetric head-to-head C-H⋯Nnitrile and C-H⋯Npyridine inter-actions, forming one-dimensional chains, which are π-stacked in an offset face-to-face fashion. The inter-molecular packing of the isomeric 6-chloro-pyridine-2-carbo-nitrile, (II), which differs only in the position of the chloro substituent on the pyridine ring, exhibits head-to-tail C-H⋯Nnitrile and C-H⋯Npyridine inter-actions, forming two-dimensional sheets which are π-stacked in an offset face-to-face fashion. In contrast to (I), the offset face-to-face π-stacking in (II) is formed between mol-ecules with alternating orientations of the chloro and nitrile substituents.