Synthesis, crystal structures and NMR and luminescence spectra of lanthanide complexes of 1,4,7,10-tetraazacyclododecane with N-methylene(phenyl)phosphinic acid pendant arms

Complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayltetramethylenet etrakis(phenylphosphinic acid) H4L1 with yttrium and a number of lanthanide s were synthesized and the crystal structures of Li[LaL1(H2O)]. 10H(2)O and Li[CeL1(H2O)]. 10H(2)O determined. The complexes are isostructural with RS RS configurations at the phosphorus atoms. The ligand is co-ordinated by fo ur nitrogen atoms in a plane and by four phosphinate oxygen atoms in a para llel plane. The planes form a twisted square prismatic co-ordination sphere . A molecule of water capping the O-4 plane completes the co-ordination sph ere of both ions. Solution properties of the complexes were investigated by H-1 and P-31 NMR. In solution six possible isomers with different configur ations on phosphorus atoms are in equilibrium. The most abundant shows the RRRS configuration. A dynamic behavior similar to lanthanide complexes of 1 ,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid is not observed. Th e NMR as well as luminescence measurements show that no water molecule is c o-ordinated directly to the lanthanide ions in solution. The ions Li(+)and Na+ form stable ion pairs with the complexes in methanol-d(4) solution as c onfirmed by the lanthanide induced shift of Li-7 and Na-23 resonances in th e presence of paramagnetic lanthanide ions. The ion pairs are not stable in aqueous solution. The alkali metal ion is located close to fourfold magnet ic axes of the complexes above the oxygen atoms and between the phenyl ring s. Luminescence spectra of [LnL(1)](-), Ln = Eu or Tb, indicate low symmetr y of the species and co-ordination number 8.