Metallacrowns (MCs) are macrocyclic complexes with a M-N-O repeating unit. They are comparable to organic crown ether molecules with an organic C-C-O repeating unit. Metallacrowns have potential uses as single-molecule magnets (SMM) and can be easily fine-tuned by reliably replacing the central cavity metal ions, bridging ligands, and countercation. The ability to deliberately manipulate and tune properties of coordination complexes is difficult in inorganic chemical syntheses; however, the self-assembled metallacrown molecules provide a platform to investigate the variation of the different molecular components. Recently it was shown that Mn[12-MCMn(III)-4] is a SMM, where a manganese(II) ion is in the central cavity. If the central manganese(II) ion was substituted with other metal ions, the magnetic behavior could change. In addition, the central metal ion is tethered to the MC framework by anionic carboxylic bridging ligands. It appears the SMM behavior of the molecules is dictated by the identity of the bridging carboxylate ligand, specifically the ligand’s pKa. If MCs are synthesized with lower pKa bridging ligands this would serve as an example in the field into alternative methods of how to purposely design SMM behavior. Lastly, the central sodium ion can be substituted with other cations and this may also alter the SMM properties of the MCs.

Synthesis of heterometallic 12-MC-4 complexes with ligand and countercation substitutions

253rd National Meeting (2017)

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