Single Isomer Heterometallic {CrIII6MII2} Rings Templated by Tetramethylammonium

A fami l y of hetero metallicrings [Me4N](2)[(Cr6M2F8)-M-III-F-II((O2CBu)-Bu-t)(16)] is reported using tetramethylammonium hydroxide pentahydrate as the source of a template, where M = Zn, Mn, Ni, and Co. The metal cores are octagons with metal-metal edges bridged by one fluoride and two carboxylate ligands. The divalent metal ions are found ordered at positions 1 and 5 in the octagon. The tetramethylammonium cations are above and below the metal plane of the ring in the crystal structure. Magnetic studies show antiferromagnetic coupling between the paramagnetic metal ions present, leading to paramagnetic ground states in each case. H-1 NMR spectroscopy confirms that the structure of the {(Cr6Co2II)-Co-III} ring exists in solution, and electron paramagnetic resonance spectroscopy confirms the magnetic structure of the other three rings.

Automated summary

A family of heterometallic rings with octagonal metal cores bridged by fluoride and carboxylate ligands has been reported, using tetramethylammonium hydroxide pentahydrate as a template source. Magnetic studies reveal antiferromagnetic coupling between different paramagnetic metal ions, resulting in paramagnetic ground states. These structures have been confirmed through H-1 NMR and electron paramagnetic resonance spectroscopy.