Syntheses and Characterizations of a Series of Novel Ln6Cu24 Clusters with Amino Acids as Ligands

With glycine or L-alanine as ligands, a series of novel 3d-4f heterometallic Ln(6)Cu(24) clusters with the formulas of [Sm(6)Cu(24)(mu(3)-OH)(30)(Gly)(12)(Ac)(12)(ClO(4))(H(2)O)(16)].(ClO(4))(9).(OH)(2).(H(2)O)(31) (1) and [Ln(6)Cu(24)(mu(3)-OH)(30)(Ala)(12)(Ac)(6)(ClO(4))(H(2)O)(12)].(ClO(4))(10).(OH)(7).(H(2)O)(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.