title: Synthesis, structures and magnetic characterizations of isostructural tetranuclear Ln4 clusters (Ln = Dy, Ho, and Eu).
abstract: Isostructural tetranuclear clusters [Ln4(salen)6]·xH2O [Ln = Dy, 1·5.5H2O; Ho, 2·4.6H2O; Eu, 3·5.2H2O; salen = N,N'-ethylenebis(salicylideneiminato)dianion] were prepared by self-assembling the corresponding lanthanide ions and a quadridentate Schiff base. Interestingly, the Ln ions are surrounded by the N- and O-donors of the Schiff bases, leading to seven- and eight-coordinate environments. The heptacoordinated Ln centers adopt a distorted capped trigonal prism, while the octacoordinated Ln atoms are in a dodecahedral disposition. The Dy complex exhibits slow magnetic relaxation, characteristic of a single-molecule magnet. Two relaxation modes in the Dy system are evident when H(dc) = 1.4 kG is applied, which is attributable to the existence of the dissimilar coordination geometries around Dy. In comparison, the Ho and Eu analogues were magnetically inspected, displaying no typical slow magnetic relaxation. These findings elucidate that the metal component in the system plays a central role in the occurrence of the magnetization relaxation process. The pronounced long-range order may contribute to intrachain exchange couplings and through-space dipolar interactions between adjacent chains.
authors.affiliation: Department of Chemistry, Korea University, Seoul 136-713, Korea.
authors.forename: Bong Ho
authors.initials: BH
authors.lastname: Koo
authors.forename: Kwang Soo
authors.initials: KS
authors.lastname: Lim
authors.forename: Dae Won
authors.initials: DW
authors.lastname: Ryu
authors.forename: Woo Ram
authors.initials: WR
authors.lastname: Lee
authors.forename: Eui Kwan
authors.initials: EK
authors.lastname: Koh
authors.forename: Chang Seop
authors.initials: CS
authors.lastname: Hong
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D004419:Dysprosium / Q000737:chemistry; D005029:Ethylenediamines / Q000737:chemistry; D005063:Europium / Q000737:chemistry; D006695:Holmium / Q000737:chemistry; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008280:Magnetics; D008968:Molecular Conformation; D012545:Schiff Bases / Q000737:chemistry; D013696:Temperature
chemical_list: D056831:Coordination Complexes; D005029:Ethylenediamines; D028581:Lanthanoid Series Elements; D012545:Schiff Bases; D004419:Dysprosium; D005063:Europium; C011452:disalicylaldehyde ethylenediamine; D006695:Holmium