Synthesis and thermal properties of IIB group derived epsilon-caprolactam-3-dithiocarboxylic acid complexes

摘要

Zn(II), Cd(II) and Hg(H) epsilon-caprolactam-3-dithiocarboxylic acid complexes were synthesized by reacting the epsilon-caprolactam-3-carbothioic sodium salt with the respective metal salt. Samples were characterized by X-ray powder diffraction, EDS elemental analysis, UV-visible, FT-IR, ~1H NMR and EPR spectroscopy. Thermal properties were determined using thermogravimetry and differential scanning calorimetric analysis. M-epsilon-caprolactam-3-dithiocarboxylic acid complexes showed intense electronic delocalization due to the charge transfer (420 nm) induced from the metal to the dithiolate group reaching different stages into the V unit (350 nm) of the dithiocarboxylate ring with a "n -> pi"(310 nm) transition. This transition was also observed by EPR which showed 3 parallel and 3 perpendicular signals. The complexes are stabilized by the electro-attraction of the amidic and carbonyl groups; the stability trend is Zn>Cd>Hg. Thermal decomposition shows a multi-step fragmentation process that suggests lactamic chain rupture.