Synthesis, spectral and kinetic studies of copper(II) thiocarboxylates as molecular precursor for metal sulfide

Abstract

A series of binary and ternary copper(II) complexes of thiocarboxylic acids and straight chain fatty acids with general formula Cu(SOCR)₂(EtOH) and Cu(SOCR)(OOCR')(EtOH) [where R = CH₃ or C₆H₅ and R' = C₇H₁₅, C₁₁H₂₃ or C₁₃H₂₇] have been synthesized and characterized. The binary copper(II) complexes have been investigated for their potential to act as precursors for the formation of metal sulfide materials. These species are expected to undergo thiocarboxylic anhydride elimination to give stoichiometric metal sulfides and remove the organic supporting ligands cleanly. The complexes are characterized by elemental and thermo gravimetric analyses, spectral (IR, UV/Visible and ESR) and molar conductivity studies, molecular weight and magnetic moment measurements. The spectroscopic and analytical data have been found to be consistent with the identified formulae and the compounds are dimeric with bridging mode of coordination of the ligands. Magnetic data and ESR studies suggest strong antiferromagnetic coupling between two copper atoms. Thermal decomposition of binary copper(II) complexes in the solid state results in the formation of CuS at low temperature as seen by powder X-ray diffraction studies. The kinetic parameters of these complexes have been investigated on the basis of the respective thermal curves. The values of the activation energy (<i>E</i>_a) of thermal decomposition, reaction order (n), frequency factor (<i>A</i>) and velocity constant (<i>k</i>)<i> </i>(in the Arrhenius kinetic equation), have been established from the thermal data. The preliminary studies reveal the great potential of this highly tailorable chemical system as precursors to metal sulfido species.