Synthesis, structure and magnetic properties of a mononuclear Cu(ii) complex with a NNO donor Schiff base ligand and its oxalato- and oxamidato-bridged dinuclear complexes

The Schiff base N,N-dimethyl-N′-propylsalicylideneimine (HL) acts as a bidentate as well as a tridentate ligand for copper(II) ions. The mononuclear complex [(HL)2Cu](ClO4)2 1 reacts with oxalate or oxamidate anions to give dinuclear complexes [(HL)Cu(μ-C2O4)Cu(HL)](ClO4)2 2, [(HL)Cu(SCN)(μ-C2O4)(SCN)Cu(HL)] 3, [LCu(μ-C2O4)CuL] 4, and [LCu{μ-(NH)2C2O2}CuL] 5. Complexes 1, 3 and 4 have been structurally characterised. Complexes 2 (previously reported) and 3 are found to be essentially square planar and square pyramidal, respectively, whereas complex 4 shows a structure intermediate between square pyramidal and trigonal bipyramidal geometry. Interconversions between 2, 3 and 4 were observed in water, depending upon the pH of the solutions. The cryomagnetic properties of 3, 4 and 5 were studied. The magnitude of the exchange coupling has been analysed in the framework of a simple orbital model.