Synthesis and characterization of a di-N-hydroxyethylated tetraaza macrocycle and its nickel(II) and copper(II) complexes: crystal structure of the nickel(II) complex

Abstract

The one-step reaction of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07,12]docosane (L1) with 2-bromoethanol produced the macrocycle 2,13-bis(2-hydroxyethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07,12]docosane (L2) in which two 2-hydroxyethyl groups are appended. The nickel(II) and copper(II) complexes of L2 have been prepared and characterized. The crystal structure of [NiL2][ClO4]2 shows that the complex is exactly centrosymmetric and the metal centre has a slightly distorted octahedral geometry with two oxygen atoms of the pendant arms at the axial positions. However, spectra and redox potentials of [CuL2][ClO4]2 indicate that the complex has a planar geometry without co-ordination of the pendant arms. The macrocycle L2 reacts more slowly with copper(II) ion than does L1 and the resulting complex dissociates very slowly even at low pH. Crystal data for [NiL2][ClO4]2: monoclinic, space group P21/n, a= 9.128(2), b= 18.141(3), c= 9.256(2)Å, β= 101.69(1)°, Z= 2, R= 0.057 and R′= 0.060 for 1993 independent reflections with I > 3σ(I).