The crystal structures of two copper(II) complexes containing the ligand di-2-pyridylamine (dpyam) with monovalent H2PO4- and divalent HPO42- oxoanions, [Cu(dpyam)(mu-H2PO4-O,O')(H2PO4)](2) (1) and [Cu(dpyam)(mu(3)-HPO4-O,O',O")],, (2), are reported and determined by X-ray crystallography. The dinuclear Cu(II) complex I was obtained by the reaction of dpyam with Cu(NO3)(2) . 3H(2)O and KH2PO4 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) Angstrom is unusually large due to the exo/endo binding of the phosphate bridges. Complex 2 is a polymeric copper(II) derivative with helical [Cu(HPO4)](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) Angstrom), from the hydrogenphosphate group weakly bound in an approximately axial position giving an extremely tetrahedrally distorted square-based pyramidal CuN2O2O' 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. (C) 2004 Elsevier B.V. All rights reserved.