Azaoxa macrocyclic complexes of lanthanide(III) thiocyanates. Crystal structures of the tris-thiocyanato (1,7,10,16-tetraoxa-4,13-diazacyclooctadecane) lanthanide(III) complexes (Ln = Eu or Yb)

The TDCO thiocyanate complexes Eu(NCS)3 TDCO and Yb(NCS)3TDCO (TDCO = 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane) have been synthesised and their X-ray structure determined. Both are monoclinic with 4 neutral molecules in the unit cell of dimensions a = 16.438(4), b = 15.211(3), c = 9.334(2)Å, β = 90.37(3)°, V = 2333.8(9) Å3, space group P2t/n for Eu and a = 17.481(3), b = 8.020(2), c = 18.056(3) Å, β = 118.12(3)°, V = 2232.6(9) Å3, space group P2t/c for Yb. They consist of nine-coordinated metal centres linked to six donor atoms of the macrocyclic ligand and to three monodentate isothiocyanate ligands situated on opposite sides of the macrocycle. The two structures present different conformations of the TDCO ligand. The mean bond lengths are EuO 2.56(2), YbO 2.498(9), EuN(ring) 2.60(1); YN(nng) 2.518(8) and EuN(CS) 2.44(1), YbN(CS) 2.365(9) Å consistent with the difference in the Eu and Yb ionic radii.