[Determination on conditional equilibrium constants of the complexes of Gd(III) and Yb(III) with HBED by UV difference spectra].
In 0.01 mol x L(-1) Hepes, pH 7.4 and at room temperature the binding of HBED with Gd(III) or Yb(III) was monitored by UV difference spectrum. The results show that the molar ratio of the complexes is most likely 1 : 1. Gd-HBED or Yb-HBED complex produced peaks at 237 nm and 291 nm. The molar absorptivities of Gd-HBED and Yb-HBED at 237 nm are deltaepsilon(Gd) = (22.52 +/- 0.20) x 10(3) cm(-1) x mol(-1) x L, deltaepsilon(Yb) = (27.15 +/- 0.11) x 10(3) cm(-1) x mol(-1) x L, respectively. The conditional equilibrium constants for the complexes were measured to be lgK(Gd-HBED) = 13.56 +/- 0.28 and lgK(Yb-HBED) = 16.06 +/- 0.03. A linear free energy relationship for the complexes of Yb(III) and Gd(III) has been established by using equilibrium data on 18 complexes. The HBED binding constants for Yb(III) and Gd (III) are in agreement with the linear free energy relationship.
Wang
Jin-Ling
JL
Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
Bi
He-Ping
HP
Yang
Bin-Sheng
BS
D000465:Algorithms; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D005682:Gadolinium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013816:Thermodynamics; D015018:Ytterbium / Q000737:chemistry*
D009942:Organometallic Compounds; C037740:N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid; D004492:Edetic Acid; D005682:Gadolinium; D015018:Ytterbium