Novel copper(II) complexes with diazamesocyclic ligands functionalized by additional donor group(s): syntheses, crystal structures and magnetic properties

Copper(II) complexes with three diazamesocyclic ligands based on 1,5-diazacyclooctane (DACO) bearing additional imidazole or phenol functional donor groups, 1,5-bis(imidazol-4-ylmethyl)- (L-1), 1-(imidazol-4-ylmethyl)- (L-2), and 1-(2-hydroxybenzyl)-1,5-diazacyclooctane (HL3), have been newly synthesized and characterized, and their structures determined by X-ray diffraction analyses. It has been revealed that with Cu(ClO4)(2). 6H(2)O L-1 forms a mononuclear complex [(CuLCl)-Cl-1]ClO4.H2O 1, L-2 forms a mu -Cl- bridged binuclear complex [(CuLCl)-Cl-2](2)[ClO4](2) 2, whereas HL3 forms a phenoxo-bridged binuclear complex [CuL3(H2O)](2)[ClO4](2) 3. Each Cu-II in the three complexes is five-coordinated in a distorted square-pyramidal environment. For the mononuclear complex 1 the Cl- anion is at the apical site, whereas for the mu -Cl--bridged binuclear complex 2 the two bridging Cl- anions occupy both the axial and one equatorial position with Cu-Cl-Cu angle 88.81(5)degrees and intramolecular Cu . . . Cu separation 3.494(8) Angstrom. In the phenoxo-bridged binuclear complex 3 the Cu-O-Cu bridging angle is 100.80(12)degrees and the intramolecular Cu . . . Cu distance is 3.0324(9) Angstrom. Variable-temperature magnetic susceptibility measurements on the two binuclear complexes 2 and 3 in the range 4.2-300 K indicate a quite different magnetic intramolecular coupling between the binuclear copper(II) centers, from a weak ferromagnetic to a very strong antiferromagnetic coupling, with 2J=1.16 (for 2) vs. -574 cm(-1) (for 3), and the magneto-structural correlations are discussed in detail. The solution behaviors of the complexes have been further studied by UV/Vis and ESR techniques.