Synthesis, crystal structure, and magnetic properties of a bis-dinuclear oxo-bridged iron(III) complex with p-sulfonatocalix[4]arene

Abstract

Reaction of sodium p-sulfonatocalix[4]arene (Na4C4AS) with iron(III) nitrate and 1,10-phenanthroline in water affords a compound in which a coordinated p-sulfonatocalix[4]arene anion (C4AS4-) bridges two oxo-bridged iron(III) dinuclear units, {FeIII2(μ-O) (H2O)5(phen)2}. The crystal structure of the compound also reveals noncoordinated C4AS4- anions and crystallization water molecules. The coordinated p-sulfonatocalix[4]arene links the {FeIII2(μ-O)(H2O)5(phen) 2} dinuclear units through two of the four sulfonate groups in the 1,2 (syn) and 1,3 (anti) modes. The complete structure may be viewed as Fe-hinged calixarene bicapsules. The study of the magnetic susceptibility reveals strong antiferromagnetic interactions between the iron(III) ions within the dinuclear units. Because the structural features of the two Fe-O-Fe oxo bridges are very similar, the magnetic data can be fitted well by considering one exchange coupling constant, J = -127(1) cm-1, which is in agreement with previously found values for oxo-bridged diiron(III) complexes with similar structural features. This opens up the possibility of polynuclear complexes stabilized in water and of control of their magnetic properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.