Ligand L (4,5-bis[(2′-hydroxyethyl)thio]1,3-dithiole-2thione) which crystallizes in the monoclinic system (P21/n) displays a 1-D network generated by a succession ofintra-molecular andinter-molecular hydrogen bonds. Weakπ-π and S⋯S interactions are also observed in the supramolecular structure. Reaction of L with one equivalent of mercury(II) iodide affords the adduct [HgI2L] (la). The crystal structure of this complex shows that coordination occurs exclusively via the sulfur atom of the thione function (C=S). The ligation on HgI2induces a change of the hydrogen bond pattern generated by the hydroxyl substituents: only intermolecular hydrogen bonds are present, organizing the adduct 1a in form of centrosymmetrical dimers in the solid state. The propensity of HgI2to build-up chains viaμ2-iodo ligand may be at the origin of the modification of the hydrogen bond network.