Synthesis, Structure, and Magnetic Properties of Phosphinate‐Bridged Hexanuclear Fe^III Complexes Containing Two Butterfly‐Shaped Fe₃O Cores

Abstract

The reaction of FeIII salts with 1,1,2,3,3‐pentamethyltrimethylenephosphinic acid [cycPO2H] or dicyclohexylphosphinic acid [(C6H11)2PO2H] along with pivalic acid in the presence of triethylamine leads to the formation of two hexanuclear iron(III) clusters: [FeIII6(μ3‐O)2(μ‐OH)2(μ‐cycPO2)6(μ‐tBuCO2)6(η1‐tBuCO2H)2]·4CH3CN·3CH2Cl2 (1) and [FeIII6(μ3‐O)2(μ‐OH)2{μ‐(C6H11)2PO2}6(μ‐tBuCO2)6(η1‐OH2)2]·2CH3CN·CH2Cl2 (2). These complexes are made up of two butterfly‐shaped {FeIII3O} subunits that are joined to each other by two bridging phosphinate ligands. In addition, the formation of 1 and 2 is assisted by μ3‐O, μ‐OH, and pivalate ligands. Variable‐temperature magnetic susceptibility measurements of complexes 1 and 2 reveal medium to strong antiferromagnetic interactions between the FeIII ions inside the Fe3O subunits and weak inter‐trinuclear antiferromagnetic interactions through the bridging phosphinate ligands. The triangular topology of the Fe3O subunits gives rise to competing antiferromagnetic interactions and spin frustration. The different relative magnitudes of the competing interactions leads to S = 5/2 and S = 1/2 ground spin states for the Fe3O subunits in 1 and 2, respectively.

Magnetic and thermodynamic properties of the octanuclear nickel phosphonate-based cage

“…Single-molecule magnets have also attracted increased interest owing to the fact that they can possibly be characterized by Heisenberg models [18,19,20,21,22,24,25,26,27,28,29,30]. Polynuclear complexes involving transition-metal and lanthanide-metal ions, synthesized from either identical or different metal ions, are amongst the themes of increasing interest in the study of molecular magnetism.…”

“…These can be properly introduced in terms of Heisenberg models such as: Fe III 6 (µ 3 − O) 2 (µ−OH) 2 {µ−(C 6 H 11 ) 2 PO 2 } 6 (µ−tBuCO 2 ) 6 (η 1 −OH 2 ) 2 ]·2CH 3 CN·CH 2 Cl 2 (for more details see Ref. [22]), and nickel containing complex Ni 8 (µ 3 − OH) 4 (OMe) 2 (O 3 PR 1 ) 2 (O 2 C t Bu) 6 (HO 2 C t Bu) 8 [18,19,20] [23].…”

“…(for more details see Ref. [22]), and nickel containing complex Ni 8 (µ 3 − OH) 4 (OMe) 2 (O 3 PR 1 ) 2 (O 2 C t Bu) 6 (HO 2 C t Bu) 8 [18,19,20] [23].…”

Bismuth and Titanium Phosphinates: Isolation of Tetra-, Hexa- and Octanuclear Clusters

“…Moreover, bismuth compounds have also been found to have a wide range of applications in catalysis, as dental materials and in human and veterinary medicine . Phosphinate ligand used to assemble transition metal based clusters have shown interesting magnetic properties . Simultaneously, polyphosphinates have been used as ligands or linkers for assembling metal organic frameworks (MOFs) .…”