Copper(II) complexes of a biphenyl-based ligand: Tuning the needs of the metal with those of the ligand

The novel pyrazole-containing tetradentate ligand 2,2'-bis[[(3,5-dimethylpyrazol-1-yl)methyl]amino]-1,1'-biphenyl (N-4-mpz), 1, was synthesized and three Cu(II) complexes, 2-4, were prepared from this compound. These complexes were characterized by a combination of elemental analysis, FAB-MS and electrochemistry and were shown to have the structure of [Cu(N-4-mpz)(Pz)]X-2 where X = BF4 or ClO4 or [Cu(N-4-mpz)(Cl)]Cl. The X-ray Structure of [Cu(N-4-mpz)(Pz)] (ClO4)(2)center dot CH3OH, 2, was determined and it showed the Cu(II) coordinated by the four nitrogen donors from the ligand along with an exogenous pyrazole donor that had been extracted from another molecule of the ligand. Cyclic voltammetry studies indicated that the complexes undergo quasi-reversible one-electron reductions in acetonitrile at potentials between 396 and 422 mV versus Ag/AgCl. (C) 2008 Elsevier Ltd. All rights reserved.