Structure and coordination properties of a tetrathiafulvalene derivative with an acetylacetone group

The synthesis and crystal structure of a new tetrathiafulvalene (TTF) derivative with an acetylacetone substituent are reported (3-(dimethylthio-TTF-thio)-2,4-pentane-dione, DMT-TTF-acac (1)). Compound 1 consists of a TTF plane and an acac plane, which are bridged by a sulfur atom. The bond distances and angles of 1 clearly indicate that the acetylacetone group adopts a keto–enol structure with an O–H⋯O intramolecular hydrogen bond. As usually observed for TTF derivatives, compound 1 exhibits two-step reversible redox waves on CV measurement, which are sensible to the metal ions being added. The stronger the metal coordination is, the larger the potential shift would be. Two complexes of 1, [M(DMT-TTF-acac)2] M = Mn(II) and Cu(II), have been prepared and they are very stable even in the state in which the ligands are oxidized. The iodine-doped compound of Mn(II) is a new organic–inorganic system consisting of paramagnetic metal ions and organic radicals.