Unusual Magnetic Behaviors and Electronic Configurations Driven by Diverse Co(II) or Mn(II) MOF Architectures

Abstract

Five novel metal organic frameworks were obtained by hydrosolvothermal reactions using the hexafluorisopropylidenebis(benzoic) acid (H2hfipbb) as linker and Co(II) or Mn(II) ions as connectors. [Co2(Hhfipbb)-(TEA)], compound 1 (TEA = triethanolamine trianion) with a threedimensional (3D) framework, and a tpu net; [Co1.5(hfipbb)2]·HN(CH2CH3)3 and [Co3(hfipbb)2]·2{HN(CH2CH3)3}, compounds 2 and 2-a, respectively, both with two-dimensional structure, sql topologies, and different layer packings. Compounds 3 and 4, having the general formula [M2(hfipbb)2]·C7H8,where M = Co (3) or Mn (4), have 3D frameworks with an sqc topology. A deep analysis of the magnetic measurements reveals different striking magnetic behaviors resulting from diverse secondary building unit and framework architectures. Compound 1 presents canted antiferromagnetic chains, compound 2 contains ferromagnetic linear trimeric clusters, and compound 3 exhibits ferromagnetic chains. For the three compounds, a 3D canted antiferromagnetic structure takes place at ∼8 K by means of weak magnetic interactions between the mentioned magnetic units. Such long-range magnetic order is precluded with the application of a high enough magnetic field. Compound 4 evidenced intrachain antiferromagnetic interactions.