Chiral Hexanuclear Ferric Wheels

The homochiral iron­(III) wheels [Fe₆{(<i>S</i>)-pedea}₆Cl₆] and [Fe₆{(<i>R</i>)-pedea)}₆Cl₆] [(<i>R</i>)- and (<i>S</i>)-<b>2</b>; pedea = phenylethylaminodiethoxide] exhibit high optical activities and antiferromagnetic exchange. These homochiral products react with each other, producing the centrosymmetric, crystallographically characterized [Fe₆{(<i>S</i>)-pedea}₃{(<i>R</i>)-pedea}₃Cl₆] diastereomer [(<i>RSRSRS</i>)-<b>2</b>]. ¹H NMR and UV–vis studies indicate that exchange processes are slow in both homo- and heterochiral systems but that, upon combination, the reaction between (<i>R</i>)- and (<i>S</i>)-<b>2</b> occurs quickly

A V₁₆-type Polyoxovanadate Structure with Intricate Electronic Distribution: Insights from Magnetochemistry

The black-green solid (NEt₄)₅­[V₁₆O₃₈(Br)]­·2H₂O (<b>1</b>) was synthesized by the pH-controlled reaction of a mixed-valence precursor (NH₄)₈­[H₉V^IV₁₂V^V₇O₅₀]­·11H₂O with Et₄NBr in water under aerobic conditions. Compound <b>1</b> crystallizes as pseudomerohedral three-domain twins with pronounced pseudosymmetry and very large voids accommodating the majority of the countercations and solvent water molecules. The central structural motif of <b>1</b> is represented by a spherical, mixed-valence, host–guest vanadium-oxo cluster [V^IV/V₁₆O₃₈(Br)]<i>^q</i> with <i>q</i> = 5–, 4–, or 6–, exhibiting dominant antiferromagnetic and weaker ferromagnetic exchange interactions. The intriguing valence-state and dependent magnetic behavior of this compound have been unraveled by weighted model Hamiltonian calculations combined with diffraction, quantum mechanical, spectroscopic, and spectrometric techniques. It appears that <b>1</b> features a hitherto not identified and initially not evident V^IV/V^V average ratio of 8:8 which corresponds to an average charge <i>q</i> = 5– of the polyoxovanadate. Our study makes a substantial contribution to the further development of methods improving the understanding of poorly soluble mixed-valence polyoxometalates with complex spin architectures