Supramolecular interactions in salts/cocrystals involving pyrimidine derivatives of sulfonate/carboxylic acid

Abstract

The crystal structures of three compounds involving aminopyrimidine derivatives are reported, namely, 5-fluorocytosinium sulfanilate–5-fluorocytosine–4-azaniumylbenzene-1-sulfonate (1/1/1), C4H5FN3O+·C6H6NO3S−·C4H4FN3O·C6H7NO3S, I, 5-fluorocytosine–indole-3-propionic acid (1/1), C4H4FN3O·C11H11NO2, II, and 2,4,6-triaminopyrimidinium 3-nitrobenzoate, C4H8N5 +·C7H4NO4 −, III, which have been synthesized and characterized by single-crystal X-ray diffraction. In I, there are two 5-fluorocytosine (5FC) molecules (5FC-A and 5FC-B) in the asymmetric unit, with one of the protons disordered between them. 5FC-A and 5FC-B are linked by triple hydrogen bonds, generating two fused rings [two R 2 2(8) ring motifs]. The 5FC-A molecules form a self-complementary base pair [R 2 2(8) ring motif] via a pair of N—H...O hydrogen bonds and the 5FC-B molecules form a similar complementary base pair [R 2 2(8) ring motif]. The combination of these two types of pairing generates a supramolecular ribbon. The 5FC molecules are further hydrogen bonded to the sulfanilate anions and sulfanilic acid molecules via N—H...O hydrogen bonds, generating R 4 4(22) and R 6 6(36) ring motifs. In cocrystal II, two types of base pairs (homosynthons) are observed via a pair of N—H...O/N—H...N hydrogen bonds, generating R 2 2(8) ring motifs. The first type of base pair is formed by the interaction of an N—H group and the carbonyl O atom of 5FC molecules through a couple of N—H...O hydrogen bonds. Another type of base pair is formed via the amino group and a pyrimidine ring N atom of the 5FC molecules through a pair of N—H...N hydrogen bonds. The base pairs (via N—H...N hydrogen bonds) are further bridged by the carboxyl OH group of indole-3-propionic acid and the O atom of 5FC through O—H...O hydrogen bonds on either side of the R 2 2(8) motif. This leads to a DDAA array. In salt III, one of the N atoms of the pyrimidine ring is protonated and interacts with the carboxylate group of the anion through N—H...O hydrogen bonds, leading to the primary ring motif R 2 2(8). Furthermore, the 2,4,6-triaminopyrimidinium (TAP) cations form base pairs [R 2 2(8) homosynthon] via N—H...N hydrogen bonds. A carboxylate O atom of the 3-nitrobenzoate anion bridges two of the amino groups on either side of the paired TAP cations to form another ring [R 3 2(8)]. This leads to the generation of a quadruple DADA array. The crystal structures are further stabilized by π–π stacking (I and III), C—H...π (I and II), C—F...π (I) and C—O...π (II) interactions.