POTENTIOMETRIC, CALORIMETRIC, AND SOLUTION NMR-STUDIES OF A TRIDENTATE LIGAND WHICH HAS A MARKED PREFERENCE FOR FORMATION OF BIS(LIGAND) VERSUS MONO(LIGAND) LANTHANIDE COMPLEXES AND WHICH EXHIBITS HIGH SELECTIVITY FOR HEAVIER LANTHANIDES

被引:83
作者
CARAVAN, P
HEDLUND, T
LIU, S
SJOBERG, S
ORVIG, C
机构
[1] UNIV BRITISH COLUMBIA,DEPT CHEM,VANCOUVER,BC V6T 1Z1,CANADA
[2] UMEA UNIV,DEPT CHEM,S-90187 UMEA,SWEDEN
关键词
D O I
10.1021/ja00150a021
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A new water-soluble N4O3 tripodal amine phenol ligand, tris(((2-hydroxy-5-sulfobenzyl)amino)ethyl)amine (H(3)TRNS) has been synthesized, and its complexation properties with six lanthanide(III) ions (Ln, Nd, Gd, Ho, Yb, Lu) have been probed. In water, the ligand coordinates in a tridentate fashion through the three phenolate oxygen atoms to give mono- and bis(ligand) complexes. The bis complexes are proposed to be 7-coordinate containing one bound water as evinced by O-17 NMR experiments on the Dy3+ complex. while the mono complexes are proposed to have a coordination number of eight or nine. The stepwise formation constants for the 1:1 and 2:1 (L:M) complexes have been measured at 25 degrees C (mu = 0.16 M NaCl) for Nd3+ (log K-1 = 6.41, log K-2 6.34), Gd3+ (log K-1 = 6.67, log K-2 = 7.69), Ho3+ (log K-1 = 7.67, log K-2 = 8.75), and Yb3+ (log K-1 = 8.53, log K-2 = 9.73). The formation constants show an increasing affinity and an unprecedented selectivity for the heavier lanthanides (beta(2(yb)) - beta(2(Nd)) = 10(5.5)). Furthermore, the stepwise stability constant for the 2:1 complex is increasingly greater than that for the 1:1 complexes of Gd3+, Ho3+, and Yb3+, while K-1 and K-2 for the 1:1 and 2:1 complexes of Nd3+ are approximately the same. Solution calorimetry shows that the selectivity for the heavier lanthanides is an enthalpic effect (Delta H-beta 2 = -45.11 (Yb) and -13.71 kJ . mol(-1) (Nd)), while the anomalous behavior in formation constants (K-2 > K-1) is predominantly entropic (Delta S-2 > Delta S-1) and is rationalized in terms of salvation of the complexes, Lanthanum(III) forms only the 1:1 complex (log K = 5.65) which precipitates from solution.
引用
收藏
页码:11230 / 11238
页数:9
相关论文
共 59 条
  • [51] Cossy C., Helm L., Merbach A.E., Inorg. Chem., 27, (1988)
  • [52] Micskei K., Helm L., Brucher E., Merbach A.E., Inorg. Chem., 32, (1993)
  • [53] Powell D.H., Gonzalez G., Tissieres V., Micskei K., Brucher E., Helm L., Merbach A.E., J. Alloys Compd., 207, 208, (1994)
  • [54] Bjerrum J., Metal Ammine Formation in Aqueous Solution, (1957)
  • [55] Maeda M., Arnek R., Biedermann G., J. Inorg. Nucl. Chem., 41, (1979)
  • [56] Cotton F.A., Wilkinson G., Advanced Inorganic Chemistry, (1980)
  • [57] Shannon R.D., Acta Crystallogr., A32, (1976)
  • [58] Kumar M., Analyst, 119, (1994)
  • [59] Liu S., Wong E., Rettig S.J., Orvig C., Inorg. Chem., 32, (1993)