MOF-like supramolecular network of Mn3 single-molecule magnets formed by extensive π–π stacking

Abstract

[Mn3O(dhb)3(mpko)3](ClO4) (4) has been obtained from the carboxylate substitution reaction of triangular [Mn3O(O2CMe)3(mpko)3](ClO4) (mpkoH=methyl(2-pyridyl)ketone oxime) with 3,5-dihydroxybenzoic acid (dhbH). Complex 4 possesses an equilateral triangle [Mn3O]7+ core with the dhb− and mpko− ligands on opposite sides of the Mn3 plane. All dhb− and mpko− groups are involved in π–π stacking interactions with those on neighboring Mn3 molecules to give a 3-D supramolecular network resembling a metal–organic framework (MOF), with periodic voids resulting from a repeating unit comprising an [Mn3]8 rhombohedron. Variable-temperature, solid-state magnetic susceptibility studies in the 5.0–300K temperature range reveal the predominance of antiferromagnetic inter-Mn3 exchange couplings. Alternating current magnetic susceptibility studies on 4 show that the single-molecule magnet (SMM) behavior characteristic of [Mn3O(O2CR)3(mpko)3]+ complexes has been lost. This work demonstrates that constructing MOF-like networks from SMMs by weak interactions is feasible but that even these can introduce significant inter-SMM exchange interactions that weaken or destroy the SMM properties.