One pot three component synthesis of mononuclear [M(1,1-dithiolato)2] {Mn(II), Co(II), Zn(II) and Cd(II)} complexes, spectral characterization, fluorescence, optical and thermogravimetric study

Abstract

A series of neutral monometallic bis-dithiocarbamate complexes, [M(1,1-dithiolato)2] {1,1-dithiolato=3-dithiocarbamato coumarin; M=Mn(II) 1, Co(II) 2, Zn(II) 3 and Cd(II) 4}, was efficiently synthesized in a single pot reaction using 3-amino coumarin, CS2 and M(OAc)2. All the complexes were characterized by microanalysis, ESI MS, FT-IR, 1H and 13C NMR, UV–Vis absorption, fluorescence, magnetic susceptibility and thermogravimetric studies. Evidently the 3-dithiocarbamato coumarin ligand behaves as monobasic bidentate in all the complexes. The electronic absorption and magnetic moment data support a distorted tetrahedral geometry around Mn(II) and a rare low spin square planar geometry around Co(II), as well as square planar Zn(II) and Cd(II) centres. The fluorescence spectra of all complexes exhibit concomitant bathochromic shifts of the intra-molecular (CT→M) charge-transfer emissions. Interestingly, the thermal decomposition of complexes 2–4 gave a metal sulfide as the final product and this indicates that these complexes may provide a single source material for the preparation of metal sulfide nanoparticles. The calculated band gap energies (Eg) fall in the range 2.039–2.565eV, suggesting the feature of a direct band gap semiconducting nature for complexes 1–4.