Direct reaction of thiazolidine-2-thione (tzdtH), an anti-thyroidal agent with diiodine in a molar ratio of 1:2 caused the heterolytic cleavage of diiodine and formation of [{(tzdtH
(1), whereas the reaction of benzothiazole-2-thione (bztzdtH) with diiodine in a molar ratio of 1:2 and 1:1 resulted in the formation of the [{(bztzdtH)I 2 }•I 2 ] (2) and [(bztzdtH)I 2 ] (3) charge-transfer (c.t.) complexes. In addition, the reaction between benzimidazole-2-thione (bzimtH) with diiodine in a molar ratio 1:2 yielded the c. 4). All reactions were carried out in dichloromethane. The molecules have been characterized by m.p., elemental analyses, and FT-Raman, FT-IR, UV/Vis and 1 H NMR spectroscopy. Crystal structures of the named complexes have been determined by X-ray diffraction at -103 °C (1), 20 °C (2 and 3) and -168 °C (4). The charge-transfer nature of the bonds of the adducts (1-4) has been verified by the lengthening of the I-I bond lengths as compared to the S-I bond lengths, by the characteristic c.t. bands observed in the UV spectra and by the shifts of frequencies measured for the I-I bond vibration in the FT-Raman spectra of the complexes. Compound 1 (C 3 H 5 NS 2 I 4 ) is monoclinic with a space group P2 1 /n and a = 9.145(2) A ˚, b = 13.259(2) A ˚, c = 10.615(2) A ˚, β = 106.30(2)°, Z = 4. The complex is ionic, containing an [a