Three new copper(II) complexes of chelidamic acid (H 3 cda) and pyrimidine derivatives, namely [Cu 2 (Hcda) 2 (ampym) 2 ]·5H 2 O (1) and [Cu 2 (Hcda) 2 (apym)(H 2 O) 2 ]·2H 2 O (2), and (Hapym) 2 [Cu(Hcda) 2 ]·4H 2 O (3) (ampym=2-amino-4-methylpyrimidine, apym=2-aminopyrimidine) have been synthesised in mild conditions starting from the proton transfer compounds (Hampym) 2 (Hcda) and (Hapym) 2 (Hcda). X-ray diffraction analysis revealed the formation of extended structures featuring dinuclear (1 and 2 with pyrimidine derivatives as metal bridges) or mononuclear (3) Hcda 2− copper(II) complex units joined via H-bonds mainly involving coordinated and lattice water molecules and the coordinated Hcda 2− ligands. Solution studies, magnetic measurements and thermal analyses were performed to fully characterise the new compounds.