Extended structures in copper(II) complexes with 4-hydroxypyridine-2,6-dicarboxylate and pyrimidine derivative ligands: X-ray crystal structure, solution and magnetic studies

Three new copper(II) complexes of chelidamic acid (H3cda) and pyrimidine derivatives, namely [Cu2(Hcda)2(ampym)2]·5H2O (1) and [Cu2(Hcda)2(apym)(H2O)2]·2H2O (2), and (Hapym)2[Cu(Hcda)2]·4H2O (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) Hcda2− copper(II) complex units joined via H-bonds mainly involving coordinated and lattice water molecules and the coordinated Hcda2− ligands. Solution studies, magnetic measurements and thermal analyses were performed to fully characterise the new compounds.