The present study deals with the crystal structures of four organic salts, namely, trimethoprim benzene sulfonate monohydrate 1, trimethoprim sulfanilate monohydrate 2, trimethoprim p-toluene sulfonate 3 and trimethoprim 3-carboxy-4-hydroxybenzene sulfonate dihydrate 4. Trimethoprim (TMP) is protonated at one of the ring nitrogens of the pyrimidine ring. Generally, in the TMP carboxylate complexes, the protonated pyrimidine ring is hydrogen-bonded to the carboxylate group forming a cyclic fork-like hydrogen-bonded bimolecular motif. In structures 1-3, the sulfonate group plays the role of the carboxylate anion. In compounds 1 and 2, there is no pairing of the pyrimidine rings because the pairing sites are blocked by water molecules donating hydrogen to the unprotonated ring nitrogen. Two of the cyclic motifs are bridged by the water molecule donating two hydrogen atoms, leading to a hydrogen-bonded supramolecular chain. This chain pairs with another chain running in the opposite direction. These two chains are cross-linked by O-H … O hydrogen bonds. In compound 2, two of the hydrogen atoms of the amino group of the sulfanilate bridge two methoxy oxygen of the two TMP cations via N-H … O hydrogen bonds resulting in a supramolecular zig-zag chain. In compound 3, two inversion related cyclic motifs are paired through a pair of N-H … N hydrogen bonds involving the 4-amino group and the N3 atom of the pyrimidine ring. In addition to the pairing, one of the sulfonate oxygen atoms bridges the 2-amino and 4-amino groups on either side of the paired bases, resulting in a self-complementary DADA (D represents the hydrogen bond donor and A represents hydrogen bond acceptor) array of quadruple hydrogen bonding patterns. In compound 4, one of the water molecules forms a hydrogen-bonded dimer with the inversion-related water molecule. The 3-carboxy-4-hydroxybenzene sulfonate moiety self-assembles into a supramolecular chain along the c axis through O-H … O hydrogen bonds. Two such oppositely running supramolecular chains are connected by dimeric and monomeric water molecules. The variation of supramolecular organization via hydrogen bonding in the four different trimethoprim sulfonate salts has been discussed.
In the title compound, trimethoprim trifluoroacetate [or 2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium trifluoroacetate], C14H19N4O3+·C2F3O2−, the trimethoprim molecule is protonated at N‐1. The carboxylate group of the trifluoroacetate anion binds with the protonated pyrimidine ring of trimethoprim (TMP) by two nearly parallel N—H⋯O hydrogen bonds. This is reminiscent of the carboxylate–trimethoprim interaction observed in dihydrofolate reductase (DHFR)–trimethoprim complexes. The pyrimidine moieties of the trimethoprim cations are centrosymmetrically paired through a pair of N—H⋯N hydrogen bonds involving the 4‐amino group and atom N3. The 2‐amino group of one TMP motif and the 4‐amino group of another motif (both of these motifs are members of a base pair) are bridged by one of the methoxy O atom of a third TMP motif, leading to a five‐membered (excluding H atoms) hydrogen‐bonded chelate. One of the H atoms of the 2‐amino group is also involved in a bifurcated hydrogen bond involving two methoxy O atoms of a trimethoprim motif, leading to a five‐membered (including the H atom) hydrogen‐bonded chelate. The pyrimidine ring makes a dihedral angle of 83.69 (10)° with the phenyl ring in the trimethoprim cation. In the trifluoroacetate moiety, the average F—C bond distance is 1.261 Å and F—C—C and F—C—F bond angles are 114.7 and 103.7° respectively.
Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(C±C) = 0.004 A Ê R factor = 0.028 wR factor = 0.061 Data-to-parameter ratio = 17.0For details of how these key indicators were automatically derived from the article, see
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