Mn(II) complexes of some acylhydrazones with NNO donor sites: Syntheses, a spectroscopic view on their coordination possibilities and crystal structures

Abstract

Mn(II) complexes derived from a set of acylhydrazones were synthesised and characterized by elemental analyzes, IR, UV-vis and X-band EPR spectral studies as well as conductivity and magnetic susceptibility measurements. In the reported complexes, the hydrazones exist either in the keto or enolate form, as evidenced by IR spectral data. Crystal structures of two complexes are well established using single crystal X-ray diffraction studies. In both of these complexes two equivalent monoanionic ligands are coordinated in a meridional fashion using cis pyridyl, trans azomethine nitrogen and cis enolate oxygen atoms positioned very nearly perpendicular to each other. EPR spectra in DMF solutions at 77 K show hyperfine sextets and in some of the complexes the low intensity forbidden lines lying between each of the two hyperfine lines are also observed.

Anti‐neurotoxic evaluation of synthetic and characterized metal complexes of thiosemicarbazone derivatives

“…However, some forbidden transitions occur and consequently, these transitions have an extremely low molar extinction coefficient value. Mn(II) complexes electronic spectra display four transitions: 6 A 1g → 4 T 1g (4G)(ν 1 ), 6 A 1g → 4 E g (4G)(ν 2 ), 6 A 1g → 4 E g (4D)(ν 3 ), and 6 A 1g → 4 T 1g (4p)(ν 4 ) . Manganese(II) complex (8) shows only a weak and broad band at 760 nm corresponding to 6 A 1g → 4 T 1g and 6 A 1g → 4 T 2g transitions that are compatible with manganese(II) ion in an octahedral environment (Figure ) .…”

Synthesis, characterization, magnetic, thermal and redox properties of oxovanadium(IV) complex of heterocyclic acid hydrazone

“…The EPR spectra of the complex have shown two sets of signals suggesting that the complex have square pyramidal geometry. As there are two sets of signals, one set (a to h) corresponding to parallel to the applied magnetic field direction (g II) and the other (1 to 8) perpendicular to the magnetic field direction (g┴), the latter set of signals, being more intense than the formal set of signals [19,20]. In the same way, there are two hyperfine splitting constants AII and A┴ for square pyramidal complexes g II < g┴, A II > A┴.…”

Anion and solvent effects on the coordination behavior of N-(2-pyridinylmethylene)benzoylhydrazone with copper(II): synthesis and structural characterization

“…Whether the coordinated hydrazone is in the keto [19] or enol [20] form depends on the reaction conditions, such as which metal ion is employed, the pH of the medium, and the nature of the hydrazone ligand [21][22][23] (Scheme 1).…”