Hydration number of tris[1-(2-thienyl) 4,4,4-trifluoro-1,3-butanedionato]lanthanoids in chloroform across the lanthanoid series

The hydration numbers of lanthanoid(III) chelates with 2-thenoyltrifluoroac etone prepared by extracting into chloroform have been determined by analyz ing the relation between lanthanoid(III) concentration and water content, T he water contents were measured by coulometric Karl Fischer titration, and the concentration of lanthanoid(III) extracted was determined by ICP/AES, T he hydration number of europium(III) chelate was also checked by measuring the luminescence lifetime, The hydration number is about 3 from lanthanum t o holmium and then decreases to about 2.4, The change reflects the variatio n in the lanthanoid(III) ionic size. The hydration number of Eu(TTA)(3) obt ained by the Karl Fischer titration agrees with that from measurement of th e luminescence lifetime, within experimental accuracy.