Antiferromagnetic Coupling in a Gadolinium(III) Semiquinonato Complex

Abstract

The strongest antiferromagnetic coupling to Gd(III) so far reported was found for the complex [Gd(Hbpz(3))(2)(dtbsq)] small middle dot2 CHCl(3) (1; Hbpz(3)=hydrotris(pyrazolyl)borate; dtbsq=3,5-di-tert-butylsemiquinonato; see structure). At 245 K the magnetic susceptibility of 1 is lower than expected for two uncorrelated spins of 7/2 and 1/2, and the lowering of chiT with increasing temperature suggests that this is due to antiferromagnetic interaction between Gd(III) and the radical.

Radical ligand-containing single-molecule magnets

“…The magnitude of J AF is determined by the degree of effective overlap between the 4f orbitals and the radical. As a result, ligands that are more strongly donating give rise to antiferromagnetic coupling, as in the case of Gd(Hbpz 3 ) 2 (dtbsq) [287]. A decrease in overlap of ligand * and 6s or 5d metal orbital also leads to observance of antiferromagnetic coupling.…”

“…The first arises from direct overlap of the radical orbitals with the 4f-orbitals, commonly leading to an antiferromagnetic interaction, and the second stems from the overlap with 5d and 6s orbitals to give a ferromagnetic interaction. Here, the former contribution was proposed to be more important for stronger donor ligands [287]. As a proof of concept, the gadolinium semiquinonate complex Gd(Hbpz 3 ) 2 (dtbsq) (27) was prepared by treating the parent Gd III benzoate derivative with 3,5-di-tertbutylcatechol and KOH (Fig.…”

Application of the Hubbard Model to Cp*2Yb(bipy), a Model System for Strong Exchange Coupling in Lanthanide Systems

“…Direct overlap is also possible in Ln complexes containing stable radicals such as nitroxyl, yet these complexes display much weaker exchange coupling. [42][43][44][45][46][47] The HMM clearly explains why exchange coupling in 1 and 3 is strong while exchange coupling between Ln centers and ligands containing stable radicals such nitroxyl radicals is much weaker. [42][43][44][45][46][47] Trivalent lanthanide ions have large, negative reduction potentials, so strongly reducing ligands with similarly large, negative reductions potentials are needed to minimize U.…”

Chemistry of the p-block elements with anionic scorpionate ligands

“…To date, only two examples of soft scorpionate complexes of aluminium are known [113], namely [Al(Bm R )Cl2] (R = Me, t Bu), synthesised by treatment of AlCl3 with LiBm R . The Xray structures reveal a tetrahedrally coordinated metal centre and the eight-membered chelate ring adopts a chair-like conformation, directing the borohydride groups away from the metal centre, rather than allowing a B -H ...M interaction as observed in other related compounds.…”