Threee 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, C10H6FNOS2, (I), and (Z)-5-(4-fluorobenzylidene)-2-thioxothiazolidin-4-one, C10H6FNOS2, (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 center dot center dot center dot O hydrogen bonds link the molecules into centro-symmetric 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, C13H13NO4S2, (III), which crystallizes with Z' = 2 in the space group P (1) over bar, 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.