The structures of different Cu(II)-thiol, dithiocarbamate, methylthiourea and amino complexes have been investigated on the basis of their spectroscopic properties. The influence of the chemical structure, both the nature of the functional groups and the spacers, on the resin chelating behaviour towards Cu(II) ions in diluted solution has been evaluated. The resins are macroporous polystyrene-divinylbenzene polymer functionalized with two spacer groups, poly(ethylene glycol) and poly(ethylene imine) chains, supporting thiol, dithiocarbamate, methylthiourea and amino groups. Electron paramagnetic resonance (EPR) was employed to show the coordination of Cu(II) ions into the complexes. Cu(II)-dithiocarbamate complexes have a square planar coordination with two dithiocarbamate groups bound to the metal. The resins with methylthiourea as functional group form Cu(II)-complexes in tetragonal symmetry with four nitrogen atoms as equatorial ligands, Further, a partial reduction of Cu(II) to diamagnetic Cu(I) with formation of Cu(I)-methylthiourea complexes, where copper is S-bonded to the methylthiourea group, could be suggested. In Cu(II)-thiol complexes, Cu(II) ions are bound through sulfur bridges. (C) 2000 Elsevier Science B.V. All rights reserved.