title: Molecular architectures for trimetallic d/f/d complexes: magnetic studies of a LnCu2 core.
abstract: Five new trinuclear Cu-Ln-Cu cluster complexes have been prepared by a one-pot reaction using H3bcn (tris- N,N',N''-(2-hydroxybenzyl)-1,4,7-triazacyclononane) and Ln = La(III), Nd(III), Gd(III), Dy(III), and Yb(III) where the d- and f-block metal ions are in close proximity desirable for magnetic studies. The [LnCu2(bcn)2]ClO4.nH2O complexes possess the same stoichiometry as the previously reported [LnNi2(bcn)2]ClO4.nH2O and [LnZn2(bcn)2]ClO4.nH2O systems. Additionally, the solid state structures of the LnCu2 complexes appear to be isostructural to the LnNi2 and LnZn2 species as determined by their nearly superimposable IR spectra. The similarities in the structures of the [LnTM2(bcn)2]ClO4.nH2O series, where TM = Zn(II), Ni(II), and Cu(II), allow for direct comparison of their magnetic exchange. An empirical approach, removing first-order anisotropic contributions determined from the analogous [LnZn2(bcn)2]ClO4.nH2O was used to study the d/f/d spin interactions in the [LnCu2(bcn)2]ClO4.nH2O complexes. A ferromagnetic exchange was determined where Ln = Gd(III), Dy(III), or Yb(III) and an antiferromagnetic exchange for Ln = Nd(III), identical to the magnetic exchange observed for the [LnNi2(bcn)2]ClO4.nH2O complexes. An exchange integral of 3.67 cm(-1) for the trimetallic [GdCu2(bcn)2]ClO4.3H2O species was determined using a modified spin Hamiltonian. The [Cu(Hbcn)] and the [Cu3(Hbcn)2](ClO4)2 building blocks of the larger coaggregated d/f/d species were also synthesized, and their structures are reported.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
authors.forename: Cheri A
authors.initials: CA
authors.lastname: Barta
authors.forename: Simon R
authors.initials: SR
authors.lastname: Bayly
authors.forename: Paul W
authors.initials: PW
authors.lastname: Read
authors.forename: Brian O
authors.initials: BO
authors.lastname: Patrick
authors.forename: Robert C
authors.initials: RC
authors.lastname: Thompson
authors.forename: Chris
authors.initials: C
authors.lastname: Orvig