Exchange Interactions on the Highest-Spin Reported Molecule: the Mixed-Valence Fe42 Complex

Abstract

The finding of high-spin molecules that could behave as conventional magnets has been one of the main challenges in Molecular Magnetism. Here, the exchange interactions, present in the highest-spin molecule published in the literature, Fe42, have been analysed using theoretical methods based on Density Functional Theory. The system with a total spin value S = 45 is formed by 42 iron centres containing 18 high-spin FeIII ferromagnetically coupled and 24 diamagnetic low-spin FeII ions. The bridging ligands between the two paramagnetic centres are two cyanide ligands coordinated to the diamagnetic FeII cations. Calculations were performed using either small Fe4 or Fe3 models or the whole Fe42 complex, showing the presence of two different ferromagnetic couplings between the paramagnetic FeIII centres. Finally, Quantum Monte Carlo simulations for the whole system were carried out in order to compare the experimental and simulated magnetic susceptibility curves from the calculated exchange coupling constants with the experimental one. This comparison allows for the evaluation of the accuracy of different exchange-correlation functionals to reproduce such magnetic properties.

Radical‐Bridged Ln4 Metallocene Complexes with Strong Magnetic Coupling and a Large Coercive Field

“…[4,5] Fory ears,ac ommon strategy to attain superior magnetic performance relied on increasing the nuclearity of transition metal complexes to isolate large spin ground state (S)intrinsic to the molecule. [6][7][8][9] As such, the energy barrier to the reversal of the magnetization (U eff ; U eff = S 2 j D j and U eff = (S 2 À 1 = 4 ) j D j for integer-a nd half-integer-spin systems,r espectively) can be increased. In this approach, the axial zerofield splitting parameter (D)w as often negligible;t hus,n o SMM behavior was attained even with remarkably high-spin ground states.I nt hese 3d complexes,t he first-order angular momentum, acontributor to the magnetic anisotropy,isoften quenched due to significant ligand field.…”

Radical‐Bridged Ln4 Metallocene Complexes with Strong Magnetic Coupling and a Large Coercive Field

“…[4,5] Fory ears,acommon strategy to attain superior magnetic performance relied on increasing the nuclearity of transition metal complexes to isolate large spin ground state (S)intrinsic to the molecule. [6][7][8][9] As such, the energy barrier to the reversal of the magnetization (U eff ; U eff = S 2 j D j and U eff = (S 2 À 1 = 4 ) j D j for integer-a nd half-integer-spin systems,r espectively) can be increased. In this approach, the axial zerofield splitting parameter (D)w as often negligible;t hus,n o SMM behavior was attained even with remarkably high-spin ground states.I nt hese 3d complexes,t he first-order angular momentum, acontributor to the magnetic anisotropy,isoften quenched due to significant ligand field.…”

H‐Mediated Magnetic Interactions between Layers in a 2D MnII–Dicyanamide Polymer: Neutron Diffraction, DFT, and Quantum Monte Carlo Calculations

“…The treatment of the periodic structure is slightly different from the approach implemented in Gaussian03. This computer code is particularly efficient for the study of magnetic properties of very large discrete systems or periodic structures , …”