Two copper(II) complexes of the saccharinate anion (sac) with piperazine (ppz) and N-(2-aminoethyl)piperazine (aeppz), namely [Cu(sac)(2)(ppz)(H2O](n) (1) and trans-[Cu(sac)(2)(aeppz)(2)] (2), have been synthesized and characterized by elemental analyses, UV-Vis, FT-IR, TGA/DTA, X-ray diffraction and magnetic measurements. The ppz ligands in 1 bridge the copper(II) centers through both nitrogen atoms to form a ID helical chain structure and the distorted trigonal-bipyramidal coordination geometry at each copper center is completed by an aqua and a pair of N-bonded sac ligands. The helical chains are linked by Ow-H center dot center dot center dot O hydrogen bonds to build a 2-D network. In complex 2, copper(II) ions are octahedrally coordinated by two sac anions and two neutral aeppz ligands, displaying a distorted octahedral coordination. Sac is O-bonded via the carbonyl group, while ppzea. acts as a N,N'-bidentate chelating ligand. The molecules are connected by N-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds, forming a linear chain. In the thermal decomposition of both complexes, the removal of the aqua and ppz or aeppz ligand takes place endothermically in the first stages and the sac moiety undergoes highly exothermic decomposition at higher temperatures to give CuO. (C) 2008 Elsevier Ltd. All rights reserved.