Coordination properties of diethyl (pyridin-2-ylmethyl)phosphate (2-pmOpe) ligand with perchlorate transition metal salts: Crystal structure of [Co(2-pmOpe)2(H2O)2](ClO4)2

A new series of the perchlorate transition-metal complexes containing the diethyl (pyridin-2-ylmethyl)phosphate (2-pmOpe) ligand of general formula [M(2-pmOpe)2(H2O)2](ClO4)2 (M = Cu, Ni, Co) were prepared. The complexes were identified and characterized by elemental analysis, spectroscopic and magnetic studies. The ligand containing two donor atoms, heterocyclic pyridyl nitrogen and phosphoryl oxygen atoms, binds in a bidentate chelate manner in all complexes. The crystal structure for [Co(2-pmOpe)2(H2O)2](ClO4)2 was determined by the X-ray diffraction method. The geometry of CoN2O4 chromophore shows an elongated octahedron, resulting from the bidentate N,O-bonded two chelate ligands and two coordinated water molecules. Every mononuclear unit is linked to other ones via two extended CoOH⋯OClO⋯HOCo bridges, forming one-dimensional (1D) hydrogen bond system. Additionally, weak CH⋯O and π–π interactions link the chains resulting in a three-dimensional (3D) (supramolecular architecture) polymeric network arrangement. Spectroscopic and magnetic results are presented in the light of the crystal structure. Magnetic data of mononuclear Co(II) compound indicate an influence of a large zero-field splitting (ZFS) and very weak intermolecular exchange interaction (zJ’ = −0.48 cm−1) on magnetic behavior. The spectroscopic and magnetic properties of Cu(II) and Ni(II) complexes indicate octahedral and mononuclear structure of both compounds.