Synthesis, crystal structure and magnetic properties of a novel tetranuclear oxo-bridged iron(III) butterfly

• [Na2(H2O)8][Fe4(μ-O)2(O2CPh)7(pic)2]2·2H2O was obtained from [Fe3O(O2CPh)6(H2O)3]+.
• Competing magnetic interactions in the {Fe4} core lead to an S = 0 ground state.
• The magnetic properties were also studied by DFT methods.

A novel carboxylate/picolinate oxo-bridged iron(III) cluster, namely [Na2(H2O)8][Fe4(μ-O)2(O2CPh)7(pic)2]2·2H2O (1) where pic = picolinate, has been obtained by reacting “basic iron benzoate” [Fe3O(O2CPh)6(H2O)3](O2CPh) with sodium picolinate in acetonitrile. The compound has been characterized by elemental analysis and IR spectroscopy and its crystal structure has been determined by single-crystal X-ray diffraction.Variable-temperature magnetic susceptibility measurements in polycrystalline samples reveal moderate antiferromagnetic couplings leading to an S = 0 ground state. Theoretically computed values of the exchange constants in the title compound were also obtained with DFT calculations and were in agreement with the overall conclusions of the analysis of the experimental data.

The novel carboxylate/picolinate oxo-bridged iron(III) cluster [Na2(H2O)8][Fe4(μ-O)2(O2CPh)7(pic)2]2·2H2O has been obtained by reacting [Fe3O(O2CPh)6(H2O)3](O2CPh) with Na(pic)·3/4H2O in acetonitrile and its crystal structure has been determined by single-crystal XRD. Variable-temperature magnetic susceptibility measurements and theoretical DFT calculations reveal antiferromagnetic interactions in a frustrated spin structure.Figure optionsDownload as PowerPoint slide