Synthesis, characterization and magnetic properties of copper(II) complexes with 4-N-(2′-pyridylimine)benzoic acid

Four Cu(II) complexes with 4-N-(2′-pyridylimine)benzoic acid (HL), [Cu(HL)2] · (ClO4)2 (1), [Cu(HL)2(SO4)] · 3H2O (2), [Cu2(L)2Cl2]n · 3H2O (3), and [Cu4(L)2(HL)2Cl4] · (CH3OH)2 · (ClO4)2 (4), have been synthesized and structurally characterized by X-ray crystallography. Complexes (1) and (2) both exhibit a mononuclear structure with a four-coordinated Cu(II) ion by the pyridine-N and imine-N atoms of the ligands for (1) and a penta-coordinated Cu(II) ion by pyridine-N, imine-N   atoms of the ligands and one oxygen atom of SO42- for (2). Complex (3) consists of a two-dimensional Cu(II) layer formed by deprotonated HL ligand linking four-membered Cu2Cl2 units. Complex (4) contains a tetranuclear Cu(II) coordination cation in which the Cu(II) ions are penta-coordinated in square pyramidal geometry by two bridging chloride atoms, two nitrogen atoms of HL ligand with undeprotonated carboxylic group, and one oxygen atom of syn,syn-carboxylato bridge. Magnetic susceptibility data show a weak ferromagnetic coupling between the Cu centers in (3) (J = 4.95 cm−1) and a weak antiferromagnetic interaction in (4) (J = −16.85 cm−1), respectively.