Supramolecular structures in three thiouracil derivatives: 5,6-trimethylene-2-sulfanylidene-1,2-dihydropyrimidin-4(3H)-one, 2-(4-fluorobenzylsulfanyl)-5,6-trimethylenepyrimidin-4(3H)-one and methyl 2-{[2-(4-fluorobenzylsulfanyl)-5,6-trimethylenepyrimidin-4-yl]oxy}acetate.

The molecules of the title compounds, C7H8N2OS, (1), C14H13FN2OS, (2), and C17H17FN2O3S, (3), crystallize in the space groups C2/m, C2/c and Ia, respectively. Compounds (1) and (2), an S-alkylated derivative of (1), consist of only one symmetry-independent molecule, while (3), an O-alkylated derivative of (2), contains two independent molecules in the asymmetric unit. The molecules of (1) sit on crystallographic mirror planes. In the supramolecular structure of (1), a combination of N-H···O and N-H···S hydrogen bonds creates a molecular strap with C(6) and R2(2)(8) motifs, which is further stabilized by an S···S contact. In the packing of (2), a one-dimensional molecular column is made up of two kinds of dimers. One dimer, with an R2(2)(18) motif, is formed by a pair of C-H···O soft hydrogen bonds and the other, with an R2(2)(8) motif, is produced via a pair of N-H···O hard hydrogen bonds. In the packing of (3), molecules A and B form two different types of one-dimensional chain by intermolecular C-H···N hydrogen bonds, and by C···N and O···S contacts, respectively. Two such kinds of chain are connected alternately via interchain C-H···O hydrogen bonds, giving a two-dimensional sheet. Finally, a three-dimensional supramolecular structure is formed through weak intersheet C-H···F hydrogen bonds. The study of the molecular and supramolecular structures of thiouracil derivatives is significant in the development of lipoprotein-associated phospholipase A2 inhibitors.