Synthesis and properties of nickel(II) and copper(II) complexes of a di-N-acetamide tetraaza macrocycle

The syntheses of the hexadentate ligand 2,13-bis(acetamido)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0(1.18),0(7.12)]docosane (L-2) and its complexes with Ni(II) and Cu(II) are described. Crystal structures of H2L2. 2HClO(4) (1), [Ni(L-2)](ClO4)(2) (2) and [Cu(L-2)](ClO4)(2) (3) are reported. The two pendant acetamide groups of the macrocyclic ligand 1 are trans to each other and the absolute configuration is a trans-IV in the solid state. The crystal structures of 2 and 3 revealed an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two oxygen atoms of the pendant acetamide groups at the axial positions. The nickel(II) and copper(II) ions are located at an inversion center. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms. (C) 2001 Elsevier Science Ltd. All rights reserved.