The coordination chemistry of mono(di-2-pyridylamine) copper(II) complexes with monovalent and divalent oxoanions: crystal structure, spectroscopic and magnetic properties of dinuclear [Cu(L)(μ-H 2PO 4)(H 2PO 4)] 2 and polynuclear [Cu(L)(μ 3-HPO 4)] n

Abstract

The crystal structures of two copper(II) complexes containing the ligand di-2-pyridylamine (dpyam) with monovalent H 2PO 4 − and divalent HPO 4 2− oxoanions, [Cu(dpyam)(μ-H 2PO 4-O,O ′)(H 2PO 4)] 2 ( 1) and [Cu(dpyam)(μ 3-HPO 4-O,O ′,O″)] n ( 2), are reported and determined by X-ray crystallography. The dinuclear Cu(II) complex 1 was obtained by the reaction of dpyam with Cu(NO 3) 2 · 3H 2O and KH 2PO 4 in a water–ethanol (45/55) mixture. The molecules are linked into dinuclear units by two bridging didentate dihydrogenphosphate groups ( endo/ exo) in an equatorial–equatorial configuration giving a slightly distorted square pyramidal stereochemistry. The Cu–Cu contact distance of 5.136(2) Å is unusually large due to the exo/ endo binding of the phosphate bridges. Complex 2 is a polymeric copper(II) derivative with helical [Cu(HPO 4)] 3 units surrounded by dpyam ligands and stabilized by intermolecular hydrogen bonds. Two nearest Cu(II) ions are bridged by a tridentate hydrogenphosphate group which is didentately coordinated to one copper(II) ion, and monodentately coordinated to another in an equatorial–equatorial configuration in an unusual bridging coordination mode. Each copper(II) ion in 2 exhibits a tetrahedrally distorted square-based geometry with the third oxygen atom (Cu–O=2.719(3) Å), from the hydrogenphosphate group weakly bound in an approximately axial position giving an extremely tetrahedrally distorted square-based pyramidal CuN 2O 2O ′ chromophore. The magnetic susceptibility measurements (5–300 K) reveals an antiferromagnetic interaction with J values of −2.85(1) and −26.20(2) cm −1 for complexes 1 and 2, respectively. Some magneto-structural trends are discussed, along with their EPR and electronic reflectance spectra and compared with those of related complexes.