Metal Ion/Buffer Interactions

摘要: The acidity constant of protonated 2-[bis(2-hydroxyethyl)amino]-2(hydroxymethyl)-1,3-propanediol (Bistris) has been measured. influence hydroxo groups on the basicity Bistris and related bases is discussed. interaction with metal ions (M2+) Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ was studied by potentiometry spectrophotometry in aqueous solution (I= 1.0 M, KNO3; 25°C) stability constants M(Bistris)2+ complexes were determined. Unexpectedly Ca(Bistris)2+ most stable among alkaline earth ion (log Kcaca(Bistris)= 2.25; corresponding values for Sr2+ Ba2+ are 0.34, 1.44 0.85, respectively). 3d series follow Irving-Williams sequence: log KMnMn(Bistris)= 0.70, Cu2+ 5.27 Zn2+ 2.38. Ternary containing ATP4- as a second ligand also investigated: Δlog KM (= KM(ATP)M(ATP)(Bistris)–log KMM(Bistris)) general negative (e.g. KCa= -0.40 or Δllog KCu= - 1.65), thus indicating that M(ATP)2- somewhat less pronounced than M2+. However, even mixed-ligand systems, complex formation may still be considerable, hence great reservations should exercised employing buffer systems ions. Moreover, several cases Km relatively high [for Mg2+-ATP4- positive], some cooperativity between coordinated ligands, possibly hydrogen-bond formation. Distributions dependence pH given, structures binary M (Bistris)2+ ternary M(ATP) (Bistris)2- participation evident.