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Direct reaction of 6‐n‐propyl‐2‐thiouracil (PTU), a widely used anti‐thyroid drug against hyperthyroidism (Graves’ disease), or 5‐chloro‐2‐mercaptobenzothiazole (CMBZTH) with iodine in a molar ratio of 1:1 resulted in the formation of the charge‐transfer (CT) complexes [(PTU)I2] (1) or [(CMBZT)I2] (2). All reactions were carried out in dichloromethane and water solutions. Compounds 1 and 2 were characterized by elemental analyses, FT‐Raman, FT‐IR, UV/Vis and 1H NMR spectroscopy. The crystal structures of both complexes were determined by X‐ray diffraction at 120(1) K (1) and 293(2) K (2). The charge‐transfer nature of the bonds in the adducts 1 and 2 was verified by the lengthening of the I−I bond lengths as compared to the S−I bond lengths and by the characteristic CT bands observed in the UV spectra of the complexes. Compound 1 [(C7H10N2OS)I2] [monoclinic with space group P21/c and a = 9.8501(7), b = 10.3101(7), c = 12.0287(8) Å, β = 99.707(6)°, Z = 4] consists of a propylthiouracil ligand bonded with an iodine atom through sulfur. Extended intermolecular N−H···O contacts link the molecules forming a supramolecular assembly. Compound 2 {(C7H4ClNS2)I2} [orthorhombic, space group P212121, a = 4.1650(10), b = 9.691(2), c = 28.471(6) Å, Z = 4] consists of a 5‐chloro‐2‐mercaptobenzothiazole ligand bonded with an iodine atom through sulfur. An extended intermolecular linkage via I···H−N bonds leads to the formation of an extended structure. Attempts to draw conclusions on the behavior of a thioamide — when used as an anti‐thyroidal drug — towards iodine have been made. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Four selenium analogues of the antithyroid drug 6-n-propyl-2-thiouracil (PTU), of formulae RSeU, (R = methyl (Me) (1), ethyl (Et) (2), n-propyl (nPr) (3), and isopropyl (iPr) 4), have been synthesized. Reaction of 1-4 with diiodine in a 1:1 molar ratio in dichloromethane results in the formation of [(RSeU)I(2)] (R = methyl (5), ethyl (6), n-propyl (7) and isopropyl (8)). All compounds have been characterized by elemental analysis, FT-Raman, FT-IR, UV/Vis, (1)H-, (13)C-, (77)Se-1D and -2D NMR spectroscopy, and ESI-MS spectrometric techniques. Recrystallization of 4 from dichloromethane afforded (4CH(2)Cl(2)). Crystals of [(nPrSeU)I(2)] (7), a charge-transfer complex, were obtained from chloroform solutions, while crystallization of 6 and 7 from acetone afforded the diselenides [N-(6-Et-4-pyrimidone)(6-EtSeU)(2)] (92 H(2)O) and [N-(6-nPr-4-pyrimidone)(6-nPrSeU)(2)] (10) as oxidation products. Recrystallization of 7 from methanol/acetonitrile solutions led to deselenation with the formation of 6-n-propyl-2-uracil (nPrU) (11). [(nPrSeU)I(2)] (7) was found to be a charge-transfer complex with a Se--I bond. These results are discussed in relation to the mechanism of action of antithyroid drugs.

The reaction of 2‐mercaptopyridine (C5H5NS or PYSH) with diiodine in a molar ratio of 1:2 in dichloromethane led to the oxidation and dimerization of the ligand and formation of [(PYS−PYSH)+·I3−]. The compound was characterised by elemental analysis, DTA‐TG, FT‐Raman, FT‐IR, UV/Vis and 1H NMR spectroscopy. The crystal structure of the complex has been determined by X‐ray diffraction at 293(2) K. The compound [(C5H4NS−SNC5H5)I3] is monoclinic with the space group P21 and a = 8.230(2) Å, b = 35.708(7) Å, c = 11.369(2) Å, β = 91.86(3)° and Z = 8. The results are discussed in relation to the mechanism of action of antithyroid drugs. The easy oxidation of PYSH by I2 to form the monocationic disulfide complex [(PYS−PYSH)+·I3−] is similar to the case of the antithyroid drug methimazole (MMI) and may indicate that PYSH might also possess antithyroid properties similar to those of MMI. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)