Supramolecular hydrogen-bonded networks in cytosinium nicotinate monohydrate and cytosinium isonicotinate cytosine dihydrate.

The title compounds are proton-transfer compounds of cytosine with nicotinic acid [systematic name: 4-amino-2-oxo-2,3-dihydropyrimidin-1-ium nicotinate monohydrate (cytosinium nicotinate hydrate), C(4)H(6)N(3)O(+) x C(6)H(4)NO(2)(-) x H(2)O, (I)] and isonicotinic acid [systematic name: 4-amino-2-oxo-2,3-dihydropyrimidin-1-ium isonicotinate-4-aminopyrimidin-2(1H)-one-water (1/1/2) (cytosinium isonicotinate cytosine dihydrate), C(4)H(6)N(3)O(+) x C(6)H(4)NO(2)(-) x C(4)H(5)N(3)O x 2 H(2)O, (II)]. In (I), the cation and anion are interlinked by N-H...O hydrogen bonding to form a one-dimensional tape. These tapes are linked through water molecules to form discrete double sheets. In (II), the cytosinium-cytosine base pairs are connected by triple hydrogen bonds, leading to one-dimensional polymeric ribbons. These ribbons are further interconnected via nicotinate-water and water-water hydrogen bonding, resulting in an overall three-dimensional network.