Synthesis and characterization of a di-N-hydroxypropylated tetraaza macrocycle and its nickel(II) and copper(II) complexes

The reaction of 5,16-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane (L1) with 3-bromo-1-propanol leads to a new macrocycle 2,13-bis(3-hydroxypropyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane (L2). [Ni(L2)]Cl2·4H2O (1), [Cu(L2)]Cl2·H2O (2) and [Cu(L2)](ClO4)2 (3) have been synthesized and characterized by X-ray crystallography and electronic absorption as well as by cyclic voltammetry. Crystal structures of 1 and 3 show that the metal ion has a square-planar geometry, coordinated by secondary and tertiary nitrogen donors of the macrocycle; however, these MN bond lengths are about 0.03 Å longer than those of [M(L1)](ClO4)2. Furthermore, 2 reveals a distorted square-pyramidal geometry with an N4 basal plane and oxygen atom of the pendant arm in the axial position. The electronic spectra, redox potentials and structures of the metal complexes are significantly affected by the presence of the pendant hydroxypropyl groups