A new series of coordination compounds of the starting materials [Cu(dienX(2)Y(2))] and their adducts [Cu(dienXXY(2))(2a-5mt)] (where then diethylenetriamine, dienXX = Schiff bases of diethylenetriamine with 2-furaldehyde or 2-thiophene-carboxaldehyde, X = O, S, Y = Cl, Br, NO3 and 2a-5mt = 2-amino-5-methylthiazole) were synthesized by stepwise reactions and their structures were established by C, H, N, Cu analysis, spectroscopic, magnetic and molar conductivity measurements. The isolated compounds are monomers, paramagnetic and electrolytic compounds of the type 1:1. In all cases, the pentadentate Schiff base (dienXX) is bonded in a tridentate fashion through the 3 N atoms. In the CudienXXY(2) compounds the coordination sphere is completed by two Cl or Br or NO3 groups in a square pyramidal arrangement. The proposed structure for this type of compound was further supported by Xray diffraction analysis of the compound [Cu(dienOO)Cl-2]. Its basal plane consists of three Cu-N contacts [2.017(2), 2.025(2) and 2.012(2) Angstrom] from dienOO, and the Cl(1) atom, while the Cl(2) atom possesses the apical position, the relevant distances being 2,2732(7) Angstrom for Cu-Cl(1) and 2.6051(7) Angstrom Cu-Cl(2). In the CudienX(2)Y(2) (.) 2a-5mt adducts the coordination sphere of copper is further completed by the nitrogen ring atom of the 2a-5mt, forming an octahedral configuration. The study of the biological activity of the compounds synthesized against a panel of different normal and cancer cell lines (MRC5, HeLa, MCF7, HT-29, OAW42, T47D) and bacteria (E coli, B. cereus, B. subtilis) showed that the adducts of the type [Cu(dienXXY(2))(2a-5mt)] exhibit increased activity both in cancer cells and in bacteria, compared to the starting material of type [Cu(dienXXY2)]. (C) 2004 Elsevier Inc. All rights reserved.