The reaction of cobalt, nickel, copper and cadmium chlorides and bromides with 5-methylfurfural thiosemicarbazone (M5FTSC) leads to the formation of two series of new complexes: [M(M5FTSC) 2 X 2 ], [M(M5FTSC)X 2 ]. They have been characterized by spectroscopic studies (infrared, 1 H NMR, and electronic spectra). The crystal structures of the free ligand M5FTSC and of the compound [CuCl 2 (M5FTSC)] have been determined by X-ray diffraction methods. For the Co(II), Ni(II) and Cu(II) complexes, the central atom is coordinated through the sulphur atom and the azomethine nitrogen atom whilst for the Cd(II) complexes, the coordination atoms are the sulphur and furanic oxygen atoms instead of the azomethine nitrogen.

3-Furaldehyde thiosemicarbazone (3FTSC) and 3-(2-furyl)prop-2-enal thiosemicarbazone (FATSC) have been prepared, their structures solved and IR, 1 H NMR spectra recorded. The thiosemicarbazone moiety in both compounds shows an E con®guration about C1±N2 and C2±N3. Intramolecular and intermolecular hydrogen bondings occur in both the molecules. The angles between the mean planes of the furanic ring and thiosemicarbazone moiety present a signi®cant difference in the two compounds. Moreover, the 1 H NMR and IR spectral studies of two compounds are quite similar.

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5-Methyl 2-furfuraldehyde thiosemicarbazone (M5HFTSC) with nickel(II) leads to three types of complexes: [Ni(M5HFTSC)(2)X(2)], [Ni(M5FTSC)(2)] and [Ni(M5FTSC)(2)] x 2DMF. In the first type the ligand remains in thione form, while in the two other, the anionic thiolato form is involved. The species [Ni(M5HFTSC)(2)X(2)] has been characterized spectroscopically. The structures of [Ni(M5FTSC)(2)] x 2DMF and [Ni(M5FTSC)(2)] have been solved using X-ray diffraction. Biological studies of [Ni(M5HFTSC)(2)Cl(2)] have been carried out in vitro for antifungal activity on human pathogenic fungi, Aspergillus fumigatus and Candida albicans, and in vivo for toxicity on mice. The results are compared to those of the ligand, the metal salt and a similar copper complex [Cu(M5HFTSC)Cl(2)].