A unique case of polymorphism in polyiodide networks resulting from the reaction of the drug methimazole and I₂

The oxidation of thioamide methimazole (C4H6N2S) with molecular diiodine in water afforded the ionic compound [2(C4H5N2S-SN2C4H6)]I3I5 (1) in 1-triclinic and 1-monoclinic polymorphs. The polymorphic nature of [C4H5N2S-SN2C4H6](2)I3I5 has been highlighted by comparing the structure of the 1-triclinic form with that of the 1-monoclinic form reported in the literature. No significant geometric differences are observed for the cations in the two polymorphs. The polymorphism is essentially due to a different arrangement in the polyiodide network of the [I-5](-) and [I-3](-) components. The FT-Raman spectrum of 1-triclinic shows the characteristic bands in the range 200-50 cm(-1) which are in good agreement with the structural features of the polyiodide network. The molecular electrostatic potential maps of the cation methimazole-disulfide [C4H5N2S-SN2C4H6](+) and the bis-cation methimazole-disulfide {[C4H5N2S-SN2C4H6](+)}(2) in 1-triclinic have been studied to clearly identify the electrostatic potential energy distributions over the cations, and the electron belt and s-hole areas responsible for the directionality of the non-covalent interactions in the polyiodides. It is suggested that the cation methimazole-disulfide may be a reaction intermediate in the inhibition of thyroid hormones by methimazole.