Acta Phys. -Chim. Sin. ›› 1994, Vol. 10 ›› Issue (04): 336-341.doi: 10.3866/PKU.WHXB19940410

• ARTICLE • Previous Articles     Next Articles

Complexation Thermodynamics of Rare Earch(III) Nitrates with Stibeno-15-Crown-5 in Anhydrous Acetonitrile

Liu Yu, Lu Tong-Bu, Tan Min-Yu, Inoue Yoshihisa, Hakushi Tadao   

  1. Lanzhou Institute of Chemical Physics Academia Sinica, Lanzhou 730000| Department of Chemistry, Lanzhou University, Lanzhou 730000| Department of Material Science,Himeji Institute of Technology, Kamigori, Hyogo 678-12| Department of Applied Chemistry, Himeji Institute of Technology, Shosha, Himeji, Hyogo 671-22, Japan
  • Received:1992-08-28 Revised:1993-03-15 Published:1994-04-15
  • Contact: Liu Yu

Abstract:

Calorimetric titrations have been performed in anthydrous acetonitrile at 298.15 K in order to obtain the complex stabillty constants(K_s) and the thermodynamic parameters for the complexation of rare earth(Ⅲ) nitrates (La, Ce, Pr, Nd, Sm, Eu) with 2,3-diphenyl-ene-(2)-1,4,7,10,13-pentaoxacyclopentadecane (Stilbeno-15-crown-5). The complexation stoichiometry is 1:1 for all rare earth(Ⅲ) nitrates. The complex stability constants (K_s), reaction enthalpies(△H~o) and entropies (△S~o) were calculated directly by using precision calorimeter connected to an personal microcomputer. The coordination of the unsaturated crown ether B (to see Fig.1) with Pr~(3+) showed the highest complexation ability and selectivity in the six kinds of rare earth (III) nitrates, and compared with the results of 15-crown-4A (in Fig.1). The thermodynamics quantities clearly indicate that the comples stability sequence is essentially entropy governed, although the complex formation itself is evidently enthalpy driven. The effects of unsaturated crown ether's molecular structure and cation's properties upon complex stability have been discussed from a viewpoint of thermodynamics.

Key words: Rare earth, Crown ether, Complexation, Thermodynamics, Calorimetric titration