INOR 532 |
| A polymer-supported diamide ligand, N,N,N',N'- tetramethylmalonamide (TMMA),is prepared for the complexation of lanthanide ions in acidic solution. It is found that polystyrene-bound TMMA exhibits high affinities for the lanthanides Eu, Tb, Ho from 6 M HCl. The distribution coefficient for the lanthanides La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in 6M HCl solution increases uniformly from La to Nd, jumps for Sm and Eu, falls at Gd, rebounds to a maximum at Tb, decreases for Dy, Ho and Er, then recovers at Tm and decreases with Yb and Lu (37.95, 56.23, 77.70, 177.26, 202.0, 185.2, 129.8, 179.5, 168.1, 167.0, 126.4 and 117.8, respectively). As a result, the lanthanide series is divided into four subgroups (La→Nd(Pm), Sm→Eu, Gd→Ho and Er→ Lu) by three breakpoints at Sm, Gd and Er. This pattern is in agreement with the tetrad effect reported for several lanthanide complexes. The trend is attributed to the process of ion recognition in which the two opposing mechanisms—the electrostatic interaction of lanthanides with the ligand which decreases with an increase in ionic radius and hydration enthalpy which increases along the series-- dominate different points so that a maximum is seen across the series. A similar trend is found in nitric acid solution but not as profound as in hydrochloric acid solution. The D values for La, Ce, Nd, Eu, Tb, Ho, Yb and Lu in 4M HNO3 solution are 151.9, 207.5, 245.2, 222.3, 275.3, 288.9, 280.0 and 206.7, respectively. This may be due to their different solvation properties. The lanthanide affinities as a function of the polymeric microenviroment is studied by anchoring the diamide ligand onto poly(glycidyl methacrylate). |
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Chemistry of Lanthanides and Actinides
2:00 PM-5:20 PM, Tuesday, August 21, 2007 BCEC -- 212, Oral
Division of Inorganic Chemistry |