Synthesis, characterization and chromotropic properties of Mn^II, Co^II, Ni^II and Cu^II with bis(acesulfamato)bis(3-methylpyridine) complexes

Abstract

The novel $[\hbox{M(acs)}_{2}($3-$\hbox{pic})_{2}(\hbox{H}_{2}\hbox{O})_{2}]$ [M: Mn^II, Co^II, and Ni^II] and $[\hbox{Cu(acs)}_{2}($3-$\hbox{pic)}_{2}]$ complexes (acs: acesulfamate; 3-pic: 3-methylpyridine) have been synthesized and characterized using elemental analyses, magnetic moments, UV–Vis and FT-IR spectra. The thermal behaviour of the complexes was also studied by simultaneous TG, DTG and DTA methods in static air atmosphere. The chromotropic properties of all complexes have been studied using thermal and spectral analysis. While the complexes of Co^II and Ni^II show reversible continuous thermochromism, an irreversible discontinuous thermochromism is observed in the Mn^II and Cu^II) complexes in the solid state. The observed thermochromism in the Mn^II, Co^II and Ni^II complexes is due to the different ligand field strength associated with the deaquation reaction. The solvatochromic behaviour of the complexes is also studied and all $[\hbox{M(acs)}_{2}(3 \hbox{-pic})_{2}]$ anhydrous complexes (except Mn^II) exhibit solvatochromic properties depending on the donor number of the solvent.