state NMR, molecular modeling, and relaxometric studies. The stability constant of Gd(OBETA) (log KGdL = 19.37, 0.1 M KCl) is 2 orders of magnitude higher than that of the higher denticity analogue Gd(EGTA) (log KGdL = 17.66, 0.1 M KCl). The half-lives (t1/2) for the dissociation reactions of Gd(OBETA) and Gd(EGTA) ([Cu2+]tot = 0.2 mM, [Cit3–]tot = 0.5 mM, [PO43–]tot = 1.0 mM, and [CO32–]tot = 25 mM at
据报道,七齿
配体OBETA(2,2'-氧双(
乙胺)-N,N,N ',N'-
四乙酸)与Ln 3+离子形成的络合物比由八齿且更流行的同类物形成的络合物更稳定
EGTA(
乙二醇ø,ö N'-双(
乙胺) - ñ,ñ,ñ ',ñ ',N'-
四乙酸)。通过X射线衍射,溶液态NMR,分子建模和弛豫分析研究了导致这种令人困惑的配位矛盾的结构特征。Gd(OBETA)的稳定常数(log K GdL= 19.37,0.1 M KCl)比高密度类似物Gd(
EGTA)高2个数量级(log K GdL = 17.66,0.1 M KCl)。Gd(OBETA)和Gd(
EGTA)解离反应的半衰期(t 1/2)([Cu 2+ ] tot = 0.2 mM,[Cit 3– ] tot = 0.5 mM,[PO 4 3– ] tot = 1.0 mM,[CO 3 2– ] tot在0.1 M KCl溶液中,pH = 7.4和25°C时的25