Synthesis, spectroscopy and magnetic properties of transition-metal complexes with diethyl [(n-butylamino-N)(pyridin-2-yl)]methylphosphonate (2-pmape): Structure of [Co(2-pmape)2](ClO4)2 complex

The compounds of general formula [ML2](ClO4)2 [M = Cu(II), Ni(II), Co(II), Zn(II)]; L = diethyl [(n-butylamino-N)(pyridin-2-yl)]methylphosphonate (2-pmape) were prepared. The stoichiometry and stereochemistry of the complexes were confirmed by elemental analysis, infrared, electronic spectral, 1H NMR, 31P NMR studies and magnetic measurements in the temperature range 1.8–300 K. The molecular structure of cobalt(II) complex, i.e. [Co(2-pmape)2](ClO4)2 was determined by the X-ray diffraction method. The complexes are six coordinate. The 2-pmape acts as N,N,O-chelate ligand. Metal ions are octahedrally surrounded by two pyridine nitrogens, two amine nitrogens and two oxygens of the phosphoryl groups from two chelating 2-pmape organic ligands. The results of the magnetic studies indicate weak intermolecular antiferromagnetic interaction between magnetic centers. The magnetic behavior of octahedral Co(II) complex is characteristic of cobalt(II) system with an important orbital contribution via spin–orbit coupling.

Graphical abstractThe perchlorate transition metal complexes with new class of aminophosphonate ligand derived from pyridine, i.e. the diethyl [(n-butylamino-N)(pyridin-2-yl)methyl]phosphonate (2-pmape) ligand were prepared and studied spectroscopically and magnetically. In particular, the molecular structure of [Co(2-pmape)2](ClO4)2 was determined by the X-ray diffraction method. The complexes are monomeric, in which 2-pmape acts as N,N,O-chelate ligand. The results of the magnetic studies indicate weak intermolecular antiferromagnetic interaction between magnetic centers.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We prepare coordination compounds of transition metals with diethyl [[(n-butylamino-N)(pyridine-2-yl)methyl]phosphonate ligand. ► The complexes are mononuclear. ► Ligand acts as N,N,O-chelate. ► The magnetic center are weakly antiferromagnetically coupled.