Magnetic Study of a Pentanuclear {Co2IIICo3II} Cluster with a Bent {CoII3} Motif

A dinuclear Co(iii)/Co(ii) complex based on the H2pmide ligand showing field-induced SMM behaviour

We report a combined computational and experimental study of the field-induced SMM behaviour of a Co(ii)/Co(iii) dinuclear complex with a pair-like H-bond intermolecular interaction.

Anisotropic exchange interaction and field-induced SMM behaviour in a mixed valence {CoCo} complex

We are reporting the synthesis and structural characterization of a new hexanuclear Co(ii)/Co(iii) complex starting from a versatile pivalate cobalt precursor and the racemic mixture of a chelating Schiff base type ligand. The main [CoII4CoIII2(μ3-OH)2(μ-OR)2(μ-OR')2(μ-OR'')2]6+ core is unprecedented and exhibits an inversion center that affords only two unique Co(ii) sites. We performed DC and AC magnetic measurements and analysed them in terms of the anisotropic exchange of ground Kramers doublets at each Co(ii) site due to their unquenched angular orbital contribution to the magnetic moment. Quantum computations support the experimental data treatment. The interplay of dominant antiferromagnetic exchange, inversion symmetry and a non-collinear main quantization axis affords an exchange energy spectrum with mostly non-magnetic states. Nevertheless, field induced SMM behaviour is observed at 1500 Oe and below 3 K which might be explained by the relaxation of the first excited magnetic state (which is populated enough) through the next closest excited state. The Orbach and/or Raman mechanism could be operative from the experimental and quantum computed results.

Structural characterization and magnetic property studies of a mixed-valence {CoIIICo} complex with a μ4-oxo tetrahedral {Co} motif

We have synthesized and structurally characterized a new mixed valence pentanuclear Co complex, bearing a rare μ4-O-tetrahedral CoII4 unit, by employing a pyridine-like Schiff base ligand. We have performed DC magnetic susceptibility and magnetization measurements over polycrystalline samples and chemical quantum computations in order to understand the exchange interaction pattern within Co(ii) sites and ground state magnetic anisotropy. This new complex shows an overall antiferromagnetic exchange interaction whose strength strongly depends on the local symmetry of Co(ii) sites. Also, local ion magnetic anisotropy reveals a strongly axial behaviour with the lowest Kramers doublet (KD) at each Co(ii) ion sufficiently isolated from excited states at low temperatures. Two Co(ii) sites show tetrahedral symmetry and the spin only formalism including axial zero-field splitting (ZFS) term properly described them; on the other hand, the other two Co(ii) sites have distorted octahedral and square base pyramidal coordination spheres, and a strong orbital contribution leads to a failure of the spin only formalism. A model of four Seff = 1/2 exchange interacting sites is necessary in order to account for low temperature magnetization behaviour. In view of the strongly anisotropic KD states, the exchange interactions are forced to be modelled as anisotropic ones. Overall, experimental data and quantum chemical computations are in good agreement, supporting the proposed model for magnetic behaviour.

Counter-complementarity control of the weak exchange interaction in a bent {Ni(ii)3} complex with a μ-phenoxide-μ-carboxylate double bridge

We report a combined computational and experimental study of a weak exchange interaction in a bent {Ni(ii)₃} complex controlled by counter-complementarity.

Slow magnetization dynamics in Co(ii)/Co(iii) triethanolamine/pivalate complexes

We report the synthesis, structural characterization and a combined computational and experimental study of the magnetic properties of two pivalate cobalt complexes, a mononuclear Co(ii) one and a tetranuclear Co(ii)₃Co(iii) mixed valence polynuclear one. The latter shows SMM behaviour revealed under an applied DC field with a thermal barrier of ca. 30 cm^-1 competing with direct and Raman relaxation processes. The Orbach thermal barrier can be understood from the doublets energy ladder arising from the anisotropic exchange interaction among ground S_eff = 1/2 of each Co(ii) sites. The strong local zero-field splitting of the S = 3/2 Co(ii) states affords these well isolated ground Kramers doublets. DC and AC magnetic susceptibility measurements as well as HF-EPR spectra support this interpretation. CASSCF quantum chemical computations have been also performed in order to aid the overall comprehension of the magnetic behaviour in the reported complexes.

Synthesis, structural characterization and magnetic behaviour of a family of [CoIII2LnIII2] butterfly compounds

We report a family of butterfly-like [CoIII2LnIII2] complexes with Ln = Gd, Tb, Dy, Ho, Er and Yb. All of them are isostructural but the complex with Ln = Gd strings in a one dimensional chain. The Dy member shows slow relaxation of magnetization under zero DC applied field, while all the others only after a small DC field is applied.

Carving a 1D CoII-carboranylcarboxylate system by using organic solvents to create stable trinuclear molecular analogues: complete structural and magnetic studies

An unprecedented strategy for the synthesis of a 1D Co^II carboranylcarboxylate polymer and their linear trinuclear derivatives.

{CoII/III5} horseshoe and {NiII4} lacunary cubane coordination clusters: the isobutyrate/N-butyldiethanolamine reaction system

A combination of carboxylate and diethanolamine-type ligands direct the formation of unusual discrete {NiII4} and {CoII/III5} structures under otherwise identical reaction conditions.

Switching nuclearity and Co(ii) content through stoichiometry adjustment: {CoII6CoIII3} and {CoIICo4III} mixed valent complexes and a study of their magnetic properties

Controlling the Co^II content in polynuclear systems: {Co^II₆Co^III₃} and {Co^IICo₄^III} mixed valent complexes with distinct magnetic behaviours is reported.