Syntheses and crystal structures of a series of heptanuclear trigonal prismatic clusters {LnCu6} (Ln ¼ La, Sm, Er) with glycine and imidazole as ligands

Three new heptanuclear trigonal prismatic polyhedra, [LnCu6(m3-OH)3(Gly)6im6](ClO4)6 (Ln ¼ La (1), Sm (2), Er (3)) were synthesized through the self-assembly of Ln3þ, Cu2þ, glycine and imidazole in aqueous solution and characterized by X-ray structure analysis. The complexes crystallize in the rhombohedral R3 space group (a ¼ b ¼ 15:9194ð5Þ A° , c ¼ 23:6190ð14Þ A°, V ¼ 5183:8ð4Þ A° 3, Z ¼ 3 (1); a ¼ b ¼ 15:8824ð3Þ A ° , c ¼ 23:4244ð5Þ A ° , V ¼ 5117:19ð17Þ A ° 3, Z ¼ 3 (2); a ¼ b ¼ 15:8774ð3Þ A ° , c ¼ 23:3428ð5Þ A ° , V ¼ 5096:15ð17Þ A ° 3, Z ¼ 3 (3)). In the cluster, Ln3þ ion is situated in the center of a prism formed by six copper atoms and coordinates to nine oxygen atoms with a tricapped trigonal prismatic coordination polyhedron. Six glycinato ligands (each adopts a h4-coordination mode and coordinates to two Cu2þ and one Ln3þ ions) and six imidazole terminal ligands (each coordinates to one Cu2þ) were used in the construction of the cluster. q 2004 Elsevier B.V. All rights reserved