Linear versus Bent 3d/4f-Heterometallic Clusters: The Carboxylate Effect on the Metal Topology and Magnetic Properties of Two {Mn^III ₂Dy₂} Complexes Supported by N-Naphthalidene-o-Aminophenol

The initial use of N-naphthalidene-o-aminophenol (naphH(2)) chelate in heterometallicclusterchemistry has provided access to two chemically similar but structurallydissimilar [Mn-III Dy-2(2)(OMe)(2)(O2CR)(6)(naph)(2)] (R = Me (1), Ph (2)) compounds with rare linear (1) and zigzag (2) topologies, respectively, dependingonly upon the ancillary carboxylate groups. The "twisted"or "bent"-like structure of 2 has mostlyaltered the Dy-III coordination geometry (square antiprismaticvs triangular dodecahedral in 1), resulting in a slightdifferentiation of the magnetic dynamics of 2 in comparisonwith 1. Direct-current (dc) magnetic susceptibility measurementsrevealed the presence of predominant antiferromagnetic exchange interactionswithin 1 and 2, while both {Mn-III Dy-2(2)} clusters exhibit out-of-phase (& chi;& DPRIME;(M)), frequency-dependent tails of signals in zero externaldc field, characteristic of the onset of the quantum tunneling ofmagnetization. Attempts to suppress the tunneling through the applicationof an external dc field were unsuccessful for a wide range of appliedfields and alternating-current (ac) frequencies. The combined resultsdemonstrate the ability of the naphH(2)/RCO2 (-) "blend" of ligands to yield new heterometalliccluster compounds with appealing structural motifs and potentiallyinteresting magnetic properties. The initialuse of the Schiff base chelate N-naphthalidene-o-aminophenol in heterometallic clusterchemistry has provided access to two chemically similar but structurallydissimilar {Mn-III Dy-2(2)} compoundswith rare linear and zigzag topologies, depending only upon the ancillarycarboxylate groups.