Bulky anion effect on the architecture of chiral dysprosium single-molecule magnets
Résumé
The interest for chiral tris(β-diketonato)lanthanide complexes in coordination chemistry is huge due to its Lewis acid character, optical activity, and the control of the final compound architecture. The reaction of equimolar quantities of [Dy((-)/(+)hfc)(3) (H(2) O)] (hfc(-) = 3-(heptafluoropropylhydroxymethylene)-(+/-)-camphorate) and L led to the formation of a pair of enantiomers for dinuclear complexes [Dy((-)/(+)hfc)(3) (L)](2) ⋅C(7) H(16) ([(-)/(+)1]⋅C(7) H(16) ) (L = 4’-(4’’’-pyridyl-N-oxide)-1,2’:6’1’’-bis-(pyrazolyl)pyridine]). Starting from the previous experimental protocol with the addition of bulky BArF anions, a partial dissociation of the chiral [Dy((-)/(+)hfc)(3) (H(2) O)] was observed leading to the isolation of a mono-dimensional cationic chiral polymer {[Dy((-)/(+)hfc)(2) (L)][BarF]}(n) ⋅nCH(3) NO(2) ([(-)/(+)2](n) ⋅nCH(3) NO(2) ). Natural circular dichroism (NCD) highlighted an exciton CD couplet for [(-)/(+)2](n) but not for (-)/(+)1. The latter behaves as a single-molecule magnet (SMM) with a blocking temperature up to 4 K, whereas [(-)/(+)2](n) is a 1D assembly of field-induced SMMs with a magnetic relaxation occurring through a Raman process only.
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