The propensity of the sp 2 sulfur atom in thiones to act as a halogen bond (XB) acceptor is well established with dihalides (I 2 , IBr or ICl) as XB donors, but has been more rarely explored with organic XB donors. The crystal structures of four iodinated heterocycles, namely, the mono-and diiodo derivatives of 1,3-dithiole-2-thione and N-ethylthiazole-2-thione, offer an opportunity to evaluate the strength and directionality of such C-I⋯S interactions. We describe here the original synthesis of 3-ethyl-5-iodothiazole-2IJ3H)-thione and 3-ethyl-4,5-diiodothiazole-2IJ3H)-thione and the solid state structures of the four compounds, with specific attention to the halogen bonds (C-I⋯SC) and hydrogen bonds (C-H⋯I,S) taking place in the crystals, in connection with the peculiarities of the calculated electrostatic surface potential (ESP) of the four molecules. The thione sulfur atoms in thiazole-2-thiones appear as better XB acceptors than in dithiole-2-thiones, with a notable deformation of the charge concentration area. The mono-iodinated derivatives, 4-iodo-1,3-dithiole-2-thione and 3-ethyl-5-iodothiazole-2-thione, are characterized by hydrogen atoms with positive extremum of the electrostatic surface potential comparable to those of the neighboring iodine atoms, illustrating the parallelism between C-I⋯S halogen bonds and the so-called weak C-H⋯I,S hydrogen bonds.
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