Mono-aqua-bridged dinuclear complexes of Cu(II) containing NNO donor Schiff base ligand: Hydrogen-bond-mediated exchange coupling

Two new mono-aqua-bridged dinuclear Cu(II) complexes of tridentate NNO Schiff bases, [Cu2(μ-H2O)L12(H2O)2](BF4)2·2H2O (1) and [Cu2(μ-H2O)L22(H2O)2](BF4)2·2H2O (2) where HL1 = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol and HL2 = 2-[(2-dimethylamino-ethylimino)-methyl]-phenol were synthesized. Both the complexes were characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. For both the complexes each Cu(II) ion is in a square-pyramidal environment being bonded to three atoms from the tridentate NNO Schiff base and a terminal H2O molecule in the equatorial plane; a second H2O ligand acts as a bridge between the two Cu(II) centres through the axial positions. Hydrogen bonds between the terminal H2O ligand and the Schiff base of the adjacent centre complete the intra-dimer linkages. Variable-temperature (4-300 K) magnetic susceptibility measurement shows the presence of significant antiferromagnetic coupling for both the complexes (J = −12.2 and −12.5 cm−1, respectively, for 1 and 2), mediated mainly through the intra-dimer H-bonds.