Facile One-Pot Route Toward Water-Soluble Lanthanide-Copper-Glycinehydroximate 15-Metallacrown-5 Complexes

Among the Ln[15MC(CuRha)-5] metallacrowns (MC; Rha = R-substituted hydroximate ligands), the simple glycinehydroximate (Glyha) complex is presented as the primary model for studying various aspects of the guest interaction with the Ln(III) ion. We report a one-pot synthesis of several glycinehydroximate LnL[15MC(CuGlyha)-5] derivatives in the presence of calcium compounds. The complexes with bidentate nitrate ion Nd(NO3)[15MC(Cu)(Glyha)(II)-5](NO3)(2) (1), bidentate acetate Y(CH3COO)[15MC(Cu)(Glyha)(II)-5](NO3)(2) (2), bridging nitrate La(NO3)[15MC(Cu)(Glyha)(II)-5](NO3)(2) (3), and bidentate lactate Gd(CH3CHOCOO)[15MC(Cu)(Glyha)(II)-5]Cl-2 [4(Gd)] have been prepared and characterized by X-ray analysis. The lactate was chosen as an example of the essential oxy-anions that exist as metabolites in all living organisms. We examined the lanthanide-induced NMR spectroscopy shifting ability of a series of lactate 4(Ln) metallacrown complexes (Ln = La, Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, or Dy). The corresponding Gd-III complex was characterized by H-1 NMR spectroscopy relaxometric techniques in aqueous media.