Preparation and Characterization of Four Strapped Tetraaza[14]annulene Copper(II) Complexes

Abstract

The reaction between a tetraaza[14]annulene copper(II) complex and four dibenzoic dichlorides led to the corresponding strapped copper(II) complexes in 21–53 % yield at 70 °C in dry toluene containing excess triethylamine. The mass spectra reveal the molecular ion signals caused by the strapped products, respectively. The infrared spectra exhibit the intense stretching mode of C=O in the 1650–1660 cm⁻¹ range and the two strong stretching modes of C-O-C at about 1250 cm⁻¹ and 1050 cm⁻¹. All elemental analyses of the strapped copper(II) complexes agree with the anticipated constitution. These copper(II) complexes assume roughly square-planar coordination based on their d→d∗ transition bands. The spin Hamiltonian parameters are consistent with those of the copper(II) complex which is not strapped which is square-planar with an unpaired electron in the d_x²-y² orbital. These results support the structure of the strapped complexes.