CRYSTAL-STRUCTURE, LUMINESCENCE AND OTHER PROPERTIES OF SOME LANTHANIDE COMPLEXES OF THE POLYPYRIDINE LIGAND 6,6'-BIS[BIS(2-PYRIDYLMETHYL) AMINOMETHYL]-2,2'-BIPYRIDINE

Europium(III) and gadolinium(III) form 1 : 1 complexes with the octade ntate polypyridine ligand s[bis(2-pyridylmethyl)aminomethyl]-2,2'-bipy ridine L(2). The crystal structure of the complex [GdL(2)Cl(2)]Cl . 2H (2)O . O.0.5EtOH has been determined. The gadolinium atom is co-ordina ted to seven nitrogen atoms of the L(2) Iigand and two chloride ligand s. One of the pyridine groups of L(2) is dangling unco-ordinated. Irra diation of water or MeOH solutions of the [EuL(2)]Cl-3 complex with UV light led to a metal-centred luminescence. The luminescence lifetimes al 296 K in water, D2O, MeOH and CD3OD were 0.78, 1.28, 0.98 and 1.25 ms, respectively. From these data the average number of co-ordinated solvent molecules (water or MeOH) was calculated to be 0.5 according t o earlier empirical correlations. The luminescence consists of a serie s of narrow lines corresponding to the envelopes of D-5(0) --> F-7(J) transitions, the most intense occurring at 613 nm (--> F-7(2)). The in tegrated intensities of these emission lines give the respective quant um yields of 0.046 and 0.089 in water and D2O. The equilibrium constan t fdr formation of the europium complex in MeOH, I = 0.100 mol dm(-3) NBu(4)ClO(4), was determined to be 10(7.09+/-0.09) dm(3) mol(-1).