Supramolecular organization via hydrogen bonding in trimethoprim sulphonate salts

Studies on hydrogen-bonding patterns playing a key role in molecular recognition and crystal engineering. Four trimethoprim derivatives were studied. In the first two there is no pairing of the pyrimidine rings being the pairing sites blocked by water donating hydrogen to unprotonated ring nitrogen. Two cyclic motifs are bridged by water leading to a hydrogen-bonded supramolecular chain. In the third compound two inversion relted cyclic motifs are paired through a pair of N-H...N hydrogen bonds. In compound four one water molecule forms a hydrogen-bonded dimer.The variation of supramolecular organisation via hydrogen-bonding in the four salts has been discussed.