Cd(II) complexes with pendant armed oxa- and azamacrocyclic ligands

Abstract

The coordination capability of the pendant-arm macrocyclic ligands – with different sizes, nature and number of the donor atoms – dioxotriaza 17-membered (L1) and pentaaza 17-membered (L2) towards nitrate and perchlorate Cd(II) salts, has been investigated. The complexes were prepared in 1:1 metal/ligand molar ratio. The characterization carried out by elemental analysis, FAB mass spectrometry, IR and NMR spectroscopy, conductivity measurements, together with the crystal structure of the complexes [CdL1(CH3CN)](ClO4)2·CH3CN and [CdL2](ClO4)2 confirms the formation of mononuclear complexes in all cases. The X-ray diffraction of [CdL1(CH3CN)](ClO4)2·CH3CN complex presents a mononuclear endomacrocyclic structure with the metal ion coordinated by the five donor atoms from the macrocyclic framework, the amine group from the pendant-arm and one acetonitrile molecule, in a distorted pentagonal bipyramid geometry. The complex [CdL2](ClO4)2 is also mononuclear, but the cadmium ion is in a distorted trigonal prism environment coordinated by the six nitrogen donor atoms from the ligand. In both cases, the perchlorate ions do not participate in the coordination to the metal ion, but they are involved in numerous hydrogen bond interactions inter- and intramolecular with phenoxy and amino-groups.