Synthesis, structural and vibrational properties of 1-(4-Fluorobenzoyl)-3-(isomeric fluorophenyl)thioureas

The 1-(4-Fluorobenzoyl)-3-(isomeric fluorophenyl)thioureas (1-3) were prepared by the reaction of 4-fluorobenzoyl isothiocyanate produced in situ with isomeric fluoroanilines in dry acetonitrile in good yields. The novel compounds were characterized by multinuclear (H-1 and C-13) NMR, elemental analyses and FTIR spectroscopy techniques. Structural and conformational properties of compounds 1-3 have been analyzed using a combined approach including X-ray diffraction, vibrational spectra and theoretical calculation methods. The carbonyl and thiourea groups are almost planar and the conformation adopted by the C=S and the C=O double bonds is antiperiplanar, in a conformation which is stabilized by intramolecular N-H center dot center dot center dot O hydrogen bond. Crystal packing shows molecules connected by intermolecular N-H center dot center dot center dot S=C hydrogen bonds to form centrosymmetric dimers. (C) 2011 Elsevier B.V. All rights reserved.