The well-studied family of single-molecule magnets, [Mn12O12(O2CR)16(H2O)4], is known to display unexpected 1H NMR spectra at room temperature. A ligand-based dynamic process causes a rapid exchange between several structural isomers of the molecule, resulting in solution NMR spectra consistent with a molecule of higher symmetry than the D2 or S4 seen in the solid state. As the temperature is lowered, this exchange is slowed down and the spectra become more complex. Using variable-temperature, multinuclear (1H, 19F, 2D) NMR spectroscopy, we were able to follow this evolution for several different [Mn12O12(O2CR)16(H2O)4] derivatives and calculate the energy barrier of the exchange process. The syntheses, NMR spectra, and interpretation of the dynamic process will be described.

Variable-temperature multinuclear NMR spectra of the [Mn12O12(O2CR)16(H2O)4] family of single-molecule magnets in solution

247th National Meeting (2014)

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