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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 17, Number 9
BKCSDE 17(9)
September 20, 1996 

Stability Constants of Divalent Transition and Trivalent Lanthanide Metal Ion Complexes of Macrocyclic Triazatri(Methylacetic Acid)
Dong Won Kim*, Choonpyo Hong, Ki-Young Choi, Chang Suk Kim, Nam-Soo Lee, Young Hun Jang, Jae Kuk Lee
The azacrown compound, 1,7-dioxa-4,10,13-triazacyclopentadecane-N,N',N"-t ri(methyl-acetic acid)(N3O2-tri(methylacetic acid)) was synthesized by modified procedure of Krespan. Potentiometric method has been used to determine the protonation constants of N3O2-tri(methylacetic acid) and stability constants of complexes on the divalent transition metal ions (Co2+, Ni2+, Cu2+, and Zn2+) and trivalent metal ions (Ce3+, Eu3+, Gd3+, and Yb3+) with N3O2-tri(methylacetic acid). The stability constants for the complexes of the divalent transition metal ions studied in the present work with N3O2-tri(methylacetic acid) were 11.4 for Co2+, 11.63 for Ni2+, 13.51 for Cu2+, and 11.65 for Zn2+, respectively. Thus, the order of the stability constants for complexes on the transition metal ions with N3O2-tri(methylacetic acid) was shown Co2+ < Ni2+ < Cu2+ > Zn2+ as same as the order of Irving-Williams series. The stability constants of Ce3+, Eu3+, Gd3+, and Yb3+ trivalent lanthanide metal ion complexes of N3O2-tri(methylacetic acid) were, respectively, 11.26 for Ce3+, 11.56 for Eu3+, 11.49 for Gd3+, and 11.80 for Yb3+. The values of the stability constants on trivalent metal ions with the ligand are increasing according to increase atomic number, due to increase acidity. But the value of stability constant of Gd3+ ion is less than the value of Eu3+ ion. This disordered behavior is also reported by Moeller.
790 - 793
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