Magnetic Properties of Diruthenium(II,III) Carboxylate Compounds with Large Zero-Field Splitting and Strong Antiferromagnetic Coupling

Abstract

The magnetic properties of mixed-valent compounds of general formula Ru2Cl(mu-O2CR)4 [R = CH2-CH3 (1), C(Me)=CHEt) (2)] have been studied in the 2-300 K temperature range. This magnetic study also includes a revision of the magnetic properties of the complex Ru2Cl(mu-O2CCMePh2)4 (3). Compounds 1-3 show a linear structure and a strong antiferromagnetic coupling between the diruthenium units through the chlorine atoms according to previous studies. Two fitting models to explain the magnetic properties of these complexes that incorporate a large zero-field splitting together with a strong antiferromagnetic coupling are described. These models consider that each diruthenium unit (S = 3/2) is magnetically coupled to the nearest diruthenium unit and ignores the longer distance magnetic coupling. The fitting models were found to be successful in fitting the magnetic data of the linear diruthenium(II,III) complexes. The zero-field splitting, D, and the antiferromagnetic coupling, zJ, vary from 37.8 to 48.0 cm-1 and from -7.43 to -13.30 cm-1, respectively, for complexes. The D values are similar to those calculated for the nonlinear diruthenium(II,III) compounds and confirm the validity of the proposed fitting models.

Synthesis, Crystal Structure, and Magnetic Properties of Amidate and Carboxylate Dimers of Ruthenium

“…There are no appreciable differences between the magnetic data of the amidate and carboxylates derivatives. The D values, ranging from 49.43 to 58.89 cm −1 , are similar to those found for analogous diruthenium complexes [3,17,18,29,30]. The low zJ values, from −0.95 to −3.62 cm −1 , are in accordance with a weak antiferromagnetic interaction between the dimetallic units mediated by the halide ligands in a zigzag chain [3,18].…”

“…The low Ru-X-Ru angles (from 101.84 • to 124.89 • ) prevent a good orbital overlap between the diruthenium units and the halide ions, leading to the weak antiferromagnetic coupling. These values are lower than that observed in other diruthenium compounds which give linear chains, in the solid state, where the electronic communication is more favored [3,17,18,29]. Although a linear correlation between the strength of the magnetic coupling and the Ru-X/Ru-X-Ru ratio has been established [18,31] compound 2 does not correlate well because the zJ is the lowest of the five compounds.…”

Polymeric, Molecular, and Cation/Anion Arrangements in Chloro‐, Bromo‐, and Iododiruthenium(II,III) Carboxylate Compounds

“…[15] Figure 2 displays the variation of the magnetic susceptibility with temperature for complex 2a. A maximum is observed at 30 K. The paramagnetic tail and the turning point have been observed previously [18,33] in diruthenium(,) complexes with linear chain structures (RuϪClϪRu angle ca. 180°).…”

“…In these cases strong antiferromagnetic coupling between the diruthenium(,) units through chlorine atoms gives rise to an inversion of the magnetic susceptibility curve and the approximation of the molecular field [14] cannot be used. Recently, we have developed a model [33] to fit this type of magnetic behaviour. A satisfactory agreement between experimentally measured and calculated curves of the molar susceptibility and the magnetic moment was obtained for complex 2a (Figure 2) by use of this model.…”

Molecular Assembly with Axial Cyanato Ligands and Paddlewheel Tetracarboxylatodiruthenium(II,III) Fragments

“…In order to estimate the zJ values, we have fitted the experimental magnetic data by using the model of Cukiernik et al, [15] which incorporates a strong ZFS as well as a weak intermolecular antiferromagnetism by the molecular field approximation. However, for complex 1 better parameters have been obtained with our model, [16] which introduces into the spin Hamiltonian the ZFS and a strong antiferromagnetic interaction. The fits of the experimental data (Figure 4) confirm the presence of a higher magnetic interaction for 1 (-5.0 cm -1 ) than for 2 (-0.1 cm -1 ).…”