Three substituted (Z)-5-benzylidene-2-thioxothiazolidin-4-ones: hydrogen-bonded dimers that can be effectively isolated or linked into chains either by aromatic pi-pi stacking interactions or by dipolar carbonyl-carbonyl interactions.

In each of the isomeric compounds (Z)-5-(2-fluorobenzylidene)-2-thioxothiazolidin-4-one, C(10)H(6)FNOS(2), (I), and (Z)-5-(4-fluorobenzylidene)-2-thioxothiazolidin-4-one, C(10)H(6)FNOS(2), (II), there is a very wide C-C-C angle (ca 130 degrees ) at the methine C atom linking the two rings. In each isomer, paired N-H...O hydrogen bonds link the molecules into centrosymmetric R(2)(2)(8) dimers; the hydrogen-bonded dimers are linked into chains by an aromatic pi-pi stacking interaction in isomer (I) and by an antiparallel dipolar carbonyl-carbonyl interaction in isomer (II). (Z)-5-(3,4,5-Trimethoxybenzylidene)-2-thioxothiazolidin-4-one, C(13)H(13)NO(4)S(2), (III), which crystallizes with Z' = 2 in the space group P-1, shows the same very wide angle at the bridging methine C atom; the two independent molecules are linked into an isolated dimer having no crystallographic symmetry.