Six new copper(II)-malonate containing complexes [Cu(dpydiol)(mal)(H2O)]·2H2O (1) (dpydiol = bis(2-pyridyl)methanediol), [Cu(dpa)(mal)(H2O)]·H2O (2) (dpa = 2,2′-dipyridylamine), [Cu(pyim)(mal)(H2O)]·H2O (3) (pyim = 2-(2-pyridyl)imidazole), [Cu(dpp)(mal)(H2O)]·3/2H2O (4) (dpp = 2,3-bis(2-pyridyl)pyrazine), [Cu(phen)(mal) (H2O)]·H2O (5), and [Cu2(phen)2(mal)(H2O)3](NO3)2·2H2O (6) (phen = 1,10-phenanthroline) were prepared and their structures were determined by single-crystal X-ray diffraction analysis. 1−5 are mononuclear complexes, whereas 6 is a dinuclear species. The neutral mono- and dinuclear units and the crystallization water molecules are linked together by hydrogen bonds to afford three-dimensional networks. In addition, π···π stacking (2, 5 and 6) and hydrophobic (4 and 6) interactions contribute to the stabilization of the structures. The analysis of the magnetic data of 6 in the temperature range 1.9–300 K shows the occurrence of a significant ferromagnetic interaction between the copper(II) ions through the carboxylate−malonate bridge [J = +6.22(1) cm−1, the isotropic spin Hamiltonian being defined as Ĥ = −JŜA·ŜB]. Funding for this work is provided by the Ministerio Español de Educación y Ciencia through projects MAT2004-03112, MAT2007-60660, CTQ2007-61690 and “Factoría de Cristalización” (Consolider-Ingenio2010, CSD2006-00015). F.S.D. acknowledges the postdoctoral fellowship of “Especialización en Organismos Internacionales” through the Spanish Ministerio de Educación y Ciencia. Peer reviewed