Tuning of Magnetic Anisotropy in Hexairon(III) Rings by Host–Guest Interactions. An Investigation by High–Field Torque Magnetometry

Magnetic anisotropy of the antiferromagnetic iron(III) rings [LiFe6(OMe)12(dbm)6]+ (I) and [NaFe6(OMe)12(pmdbm)6]+ (II), where Hdbm=1,3-diphenyl-1,3-propanedione and Hpmdbm=1,3-di(4-methoxyphenyl)-1,3-propanedione, was investigated. Staircase structures were obsd. on the torque curves of I-PF6 and II-ClO4 and were assigned to spin-level crossings from the spin ground state. The host-guest interactions responsible for the large difference in magnetic coupling also yield a dramatic difference in the magnetic anisotropies.