Ferrocenyl-substituted nitronyl nitroxide in the design of one-dimensional magnets

Abstract

By the reaction of M(hfac)₂ (M = Mn(II), Co(II), Cu(II), and Zn(II); hfac is the hexafluoroacetylacetonate anion) and ferrocenyl-substituted nitronyl nitroxide (L), we succeeded in the synthesis of stable heterospin complexes: mononuclear [Zn(hfac)₂L], trinuclear {[Cu(hfac)₂]₃L₂} and chain polymer [Mn(hfac)₂L]_n and [Co(hfac)₂L]_n. The specific steric bulkiness of the ferrocenyl substituent leads to the formation of trans-type coordination polyhedra in the [Mn(hfac)₂L]_n and [Co(hfac)₂L]_n chains. The introduction of the ferrocene substituent leads to an effective weakening of intermolecular or interchain magnetic exchange coupling. Ferrimagnetic ordering was observed for one-dimensional complexes [M(hfac)₂L]_n (M = Mn(II), Co(II)). [Co(hfac)₂L]_n exhibits features of single-chain magnet behaviour: slow relaxation of magnetization below 13 K is associated with a high coercive field (54 kOe at 2 K).