Syntheses and characterizations of a series of novel Ln(6)Cu(24) clusters with amino acids as ligands

Abstract

With glycine or L-alanine as ligands, a series of novel 3d-4f heterometallic Ln(6)Cu(24) clusters with the formulas of [(SmCu24)-Cu-6(mu(3)-OH)(30)(Gly)(12)(Ac)(12)(ClO4)(H2O)(16)](ClO4)(9)(.)(OH)(2)(.)(H2O)(31) (1) and [Ln(6)Cu(24)(mu(3)-OH)(30)(Ala)(12)(Ac)(6)(ClO4)(H2O)(12)](.)(ClO4)(10)(.)(OH)(7)(.)(H2O)(34) (2(.)Ln) (Ln = Tb, Gd, Sm, and La) were synthesized by self-assembly, among which 1 and 2(.)Tb were characterized by X-ray structure analysis. The metal skeleton of the clusters may be described as a huge {Ln(6)Cu(12)} octahedron (constructed with 6 Ln(III) ions located at the vertices and 12 inner Cu-II ions located at the midpoints of the edges) connected by 12 additional Cu-II ions (every 2 are connected to 1 Ln(III) vertex). The temperature dependence of the magnetic susceptibilities of 2(.)Ln was investigated and was found to vary with the central rare-earth ions. Impedance spectroscopic measurements of 2(.)Ln reveal that they are ionic conductors.