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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 12, Number 2
BKCSDE 12(2)
February 20, 1991 

New Cryptand Complexes of Lanthanides(Ⅲ) and Dioxouranium(Ⅵ) Nitrates
Oh-Jin Jung*, Chil-Nam Choi, Hak-Jin Jung
The following new cryptand 221 complexes of lanthanides(Ⅲ) and dioxouranium(Ⅵ) nitrate have been synthesized: (Ln(C16H32N2O5)(H2O)2(NO3)3 and ((UO2)2(C16H32N2O5)(H2O)4(NO3)4. These complexes have been identified by elemental analysis, moisture titration, conductivity measurements and various spectroscopic techniques. The proton and carbon-13 NMR as well as calorimetric measurements were used to study the interaction of cryptand 221 with La(Ⅲ), Pr(Ⅲ ), Ho(Ⅲ) and UO2(Ⅱ) ions in nonaqueous solvents. The bands of metal-oxygen atoms, metal-nitrogen atoms and O-U-O in the IR spectra shift upon complexation to lower frequencies, and the vibrational spectra (δNMN) of metal-amide complexes in the crystalline state exhibit lattice vibrations below 300 cm-1. The NMR spectra of the lanthanides(Ⅲ) and dioxouranium(Ⅵ) nitrate complexes in nonaqueous solvents are quite different, indicating that the ligand exists in different conformation, and also the 1H and 13C-NMR studies indicated that the nitrogen atom of the ring has greater affinity to metal ions than does the oxygen atom, and the planalities of the ring are lost by complexation with metal ions. Calorimetric measurements show that cryptand 221 forms more stable complexes with La3+ and Pr3+ ions than with UO22+ ion, and La3+/Pr3+ and UO22+/Pr3+ selectivity depends on the solvents. These changes on the stabilities are dependent on the basicity of the ligand and the size of the metal ions. The absorption band (230-260 nm) of the complex which arises from the direct interaction of macrocyclic donor atoms with the metal ion is due to n-δ* transition and also that (640-675 nm) of UO22+-cryptand 221 complex, which arises from interaction between two-dioxouranium(Ⅵ) ions in being out of cavity of the ligand ring is due to d-d* transition.
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