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

Three new heptanuclear trigonal prismatic polyhedra, [LnCu(6)(mu(3)-OH)(3)(Gly)(6)im(6)](ClO4)(6) (Ln = La (1), Sm (2), Er (3)) were synthesized through the self-assembly of Ln(3+), Cu2+, glycine and imidazole in aqueous solution and characterized by X-ray structure analysis. The complexes crystallize in the rhombohedral R3 space group (a = b = 15.9194(5) Angstrom, c = 23.6190(14) Angstrom, V = 5183.8(4) Angstrom(3), Z = 3 (1); a = b = 15.8824(3) Angstrom, c = 23.4244(5) Angstrom, V = 5117.19(17) Angstrom(3), Z = 3 (2); a = b = 15.8774(3) Angstrom, c = 23.3428(5) Angstrom, V = 5096.15(17) Angstrom(3), Z = 3 (3)). In the cluster, Ln(3+) 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 eta(4)-coordination mode and coordinates to two Cu2+ and one Ln(3+) ions) and six imidazole terminal ligands (each coordinates to one Cu2+) were used in the construction of the cluster. (C) 2004 Elsevier B.V. All rights reserved.