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

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.

Graphical abstractMn(II) complexes synthesised using four different tridentate NNO donor acylhydrazones have been characterized by elemental analyzes, spectroscopic techniques, magnetic susceptibility and molar conductivity measurements. It was found that on complexation the hydrazones can exist both in keto and in enolate form which is evident from the IR spectra of the complexes. We could successfully isolate single crystals of two of the complexes and Mn was found to be in a distorted octahedral geometry.Figure optionsDownload full-size imageDownload as PowerPoint slide