三元混配配合物的稳定性研究(Ⅷ).Pt(Ⅱ)-UTP-ArL体系

Study on stability of the ternary mixed-ligand complexes(Ⅷ) of Pt(Ⅱ)-UTP-ArL

用pH电位滴定法测定了铂( )与尿苷5′-三磷酸和另一芳环系列配体ArL形成的三元混配配合物Pt(ArL)(UTP)n-(ArL=Phen,Bpy和Trp;n=2或3)在水溶液中的稳定常数(I=0.1mol/L,KNO3;25℃).用ΔlgKM比较了二元和三元混配配合物的稳定性差异,认为三元混配配合物稳定性的增加可归因于π-酸-π-碱之间的合作效应和分子内芳环配体的堆积作用,后者和参与堆积的芳环大小一致,即稳定性Pt(Phen)(UTP)2->Pt(Bpy)(UTP)2->Pt(Trp)(UTP)3-.

The stability constants of the binary complexes Pt(UTP)^(2-), Pt(Trp)^+, and the ternary mixed-ligand complexes Pt(ArL)(UTP)^(n-)(ArL=Phen, Bpy and Trp; n=2 or 3) have been determined by pH titration in dilute aqueous solution (I=0.1 mol/L, KNO_3; 25 ℃). The difference of stability between the binary and the ternary complexes has been compared by ΔlgK_(Pt). It is suggested that the increasing stability in the ternary mixed-ligand complexes is explained by the cooperative effect of πacid-πbase and the intramoleculer aromatic-ring stacking interaction, which is in accord with the size of aromatic-ring forming stacks. The order of stability of the ternary mixed-ligand complexes is Pt(Phen)(UTP)^(2-)>Pt(Bpy)(UTP)^(2-)>Pt(Trp)(UTP)^(3-).