Synthesis, Thermal, Magnetic Properties and Crystal Structure of Homodinuclear Copper(II) Complexes with New `End-off' Compartmental Schiff Bases

The homodinuclear copper(II) complex Na2 [Cu2- Lc(OH)(H2O)2]·11H2O (H5Lc is the Schiff base derived from the condensation of 2,6-diformyl-4- chlorophenol and (View the MathML source)1-aminoethanephosphonic acid in a 1:2 molar ratio) has been prepared and characterized by IR, UV data, scanning electron microprobe analysis and X-ray diffraction. The crystal structure of Na2 [Cu2Lc(OH)(H2O)2]·11H2O has been determined by X-ray crystallography and refined to the final R of 0.032. The compound is triclinic, space group PView the MathML source, with a = 17.129(5), b = 11.558(5), c = 8.372(5) Å, ? = 95.95(3), ? = 104.72(3), and ? = 76.21(3)°; Z = 2. The compound is a dinuclear complex in which the copper ions are five-coordinate square pyramidal. One oxygen atom from the pentadentate pentaanionic ligand and the OH-oxygen provide bridging of the metal ions. Two water molecules are in the apical positions. The sodium ions are octahedrally surrounded by oxygen atoms from water and phosphonate groups. Selected bond distances are: Cu?O(base) 1.92 to 1.98 Å; Cu?N 1.97 Å; Cu?O- (axial) 2.51 and 2.28 Å; Na-?O(water) 2.38 to 2.50 Å; Na?O(phosphonate) 2.57 Å. The crystal lattice is stabilized by an extensive network of hydrogen bonds. The thermal and magnetic behaviour over 68-290 K temperature range are reported together with a comparison with the analogous homodinuclear copper(II) complex with the ligand H3LA (H3LA is the Schiff base derived from the condensation of 2,6- diformyl-4-chlorophenol and aminomethanesulphonic acid in a 1:2 molar ratio). The two copper(II)ions exhibit a significant antiferromagnetic interaction (J = -202.5 cm-1).