Molecular architectures for trimetallic d/f/d complexes:: Structural and magnetic properties of a LnNi2 core

A series of cationic, trimetallic d/f/d complexes have been prepared which use a multiclentate, macrocyclic amine phenol ligand to coordinate divalent first row d-block transition metal ions (TM) and lanthanides (Ln) ions in close proximity, desirable for magnetic studies. Isolable complexes of the d/f/d cluster compounds with the formula [Ln(TM)(2)(bcn)(2)]ClO4 center dot nH(2)O, where H(3)bcn is tris-N,N'N-(2-hydroxybenzyl)-1,4,7-triazacyclononane, TM = Zn(II) and Ni(II) and Ln = La(III), Nd(III), Gd(III), Dy(III), and Yb(III), were synthesized by a one-pot sequential reaction of stoichiometric amounts of H3bcn with the TM(11) and Ln(111) metal ions. The spontaneously formed cationic complexes were characterized by a variety of analytical techniques including IR, NMR, +ESI-MS, and EA. The [TM(Hbcn)]center dot nH(2)O and [TM3(bcn)(2)]center dot nH(2)O complexes were also synthesized to probe the building blocks of the d/f/d coaggregated species. The solid-state X-ray crystal structures of [GdNi2(bcn)(2)(CH3CN)(2)]ClO4 center dot CH3CN and [GdZn2(bcn)(2)(CH3CN)(2)]ClO4 center dot CH3CN were determined to be nearly identical with each TM(11) encapsulated in an octahedral geometry by the N3O3 binding pocket of the bcn(3-) ligand. The eight coordinate Gd(111) was bicapped by two [TM(bcn)](-) moieties and coordinated by two solvent molecules. Because of the isostructurality of the [LnZn(2)(bcn)(2)]ClO4 center dot nH(2)O and [LnNi(2)(bcn)(2)]ClO4 center dot nH(2)O complexes, an empirical approach using the LnZn(2) magnetic data was utilized to remove first-order anisotropic contributions from the LnNi2 species. Ferromagnetic spin interactions were determined for the [LnNi(2)(bcn)(2)]ClO4 center dot nH(2)O complexes, where Ln = Gd(III), Dy(III), and Yb(III), while an antiferromagnetic exchange was observed for Ln = Nd(III).