Reaction of N-methylbenzothiazole-2-thione (C8H7NS2 or NMBZT) with diiodine produced the charge-transfer (ct) complex [(NMBZT) (.) I-2(1). NMBZT reacts with diiodine in the presence of FeCl3 in a molar ratio of 3:6:1 and forms the ionic complex {[(NMBZT)(2)I+]center dot[FeCl4](-)] (2) together with {[(NMBZT)(2)I(+)center dot[I-7](-)} (2a) iodonium salt. The reaction of benzimidazole-2-thione (C7H6N2S or MBZIM) with diiodine on the other hand results in the formation of the ct {[(MBZIM)I-2](+)[I-3](-)}center dot[(MBZIM)center dot I-2] (3) compound. The compounds have been characterized by elemental analyses, DTA-TG, FT-Raman, FT-IR, UV-vis, and H-1 NMR spectroscopies, and X-ray crystal structure determinations. Compound 1, C8H7I2NS2, is orthorhombic with a space group Pna2(1) and a = 12.5147(13) angstrom, b = 22.536(3) angstrom, c = 4.2994(5) angstrom, and Z = 4. Compound 2, C16H14Cl4FeIN2S4, is monoclinic, space group C2/c, a 35.781(2) angstrom, b = 7.4761(5) angstrom, c = 18.4677(12) angstrom, beta = 107.219(1)degrees, and Z = 8. Compound 3, C21H18I6N6S3, monoclinic, space group P2(1)/n, a = 14.0652(11) angstrom, b = 22.536(3) angstrom, c = 4.2994(5) angstrom, beta = 99.635(7)degrees, and Z = 4, consists of two component moieties cocrystallized, one neutral which contains the benzimidazole-2-thione (MBIZM) ligand bonded with an iodine atom through sulfur, forming a compound with a "spoke" structure [(MBZIM)I-2] 3a, while the other is the ionic complex {[(MBZII)(2)I+}center dot[I-3](-)} (3b). The X-ray crystal structure of 1 shows a bond between the thione-sulfur atom and one of the iodine atoms in an essentially planar arrangement. In the cation of 2, an iodine is coordinated by two thione-sulfur atoms in a linear arrangement but the molecule is not planar. For the first time in the solid state a spoke-ionic mixed complex has been characterized in 3. One component of the structure is a molecular diiodine adduct, i.e., [(MBZIM)I-2] (3a), with a linear coordination geometry in a decidedly planar arrangement, and the other component is an ionic adduct {[(MBZIM)(2)I](+)center dot[I-3](-)] (3b) with the cation having an arrangement similar to that found for 1. Theoretical calculations using density functional (DFT) and ab initio Hartree-Fock theory have been carried out for I and 3a,b. The results are consistent with the experimental data. Conclusions on the behavior of a thioamide, when used as an antithyroid drug, have also been made.