Cd(II) complexes with N8 and N4O4 donor macrocyclic ligands

The coordination capability of the octaaza 24-membered (L1) and the tetraoxotetraaza 28-membered (L2) macrocycle ligands – with different sizes, nature and number of the donor atoms – has been investigated with nitrate and perchlorate Cd(II) salts. The complexes were prepared in 1:1 and 2:1 Cd:L molar ratio. The characterization by elemental analysis, IR, LSI mass spectrometry, conductivity measurements and 1H NMR spectroscopy, together with the crystal structure of the complexes [CdL1](NO3)2 · 0.5H2O, [CdL1](ClO4)2 and [CdL2(CH3CN)2](ClO4)2 · CH3CN · H2O confirms the formation of mononuclear complexes in all cases. The [CdL1](NO3)2 · 0.5H2O and [CdL1](ClO4)2 present a mononuclear endomacrocyclic structure with the metal ion coordinated by the eight donor nitrogen atoms from the macrocyclic backbone in a square antiprism geometry. The complex [CdL2(CH3CN)2](ClO4)2 · CH3CN · H2O is also mononuclear, but the cadmium ion is in an octahedral environment coordinated by four amine nitrogen atoms from the macrocyclic framework and two nitrogen atoms from two acetonitrile molecules. The ether oxygen atoms from the ligand are not coordinated.