The preparation, characterization and crystal structures of the mono(dpyam) copper(II)nitrato complexes [Cu(dpyam)(O2NO)(2)] (1) and [Cu(dpyam)(O2NO)(2)].2H(2)O (2) (dpyam = di-2-pyridylamine) have been investigated. Compound 1 consists of two crystallographically independent [Cu(dpyam)(O2NO)(2)] neutral molecules. These molecules are linked into infinite chains by the bridging bidentate nitrate groups in the long-bonded tetragonal positions giving an elongated rhombic octahedral stereo chemistry. The structure of 2 is composed of a couple of crystallographically independent [Cu(dpyam)(O2NO)(2)] neutral molecules and four water molecules in the lattice. Each copper atom exhibits a tetrahedrally distorted square base of the N2O2 plane, with the second oxygen atoms of the monodentate nitrato groups weakly bound in nearly axial positions giving an extremely distorted octahedral coordination geometry. (C) 2002 Elsevier Science Ltd. All rights reserved.