Spin Flip Excitonic States in Molecular Magnets

Recent work on Mn₃, Mn(taa), and [Mn^IIIMn^III]³⁺ triplesalen provide substantial evidence that the presence of single ion S=1 states can be energetically more stable [1,2,3]. Based on these studies, we looked for the presence of S=1 centers, referred to here as Spin Flip Excitons (SFEs), in the Mn₁₂O₁₂(COOR)₁₆[H₂O]₂ (Mn₁₂-Ac) single-molecule magnet. Through DFT calculations, our results show that we can indeed get up to eight electronically stable low energy excitons states. The total spin of the structures reduces to S=6 and S=2 when four and eight Mn atoms carry a spin of S=1. There are significant changes in the moment of the outer Mn atoms and the bond length between Mn-OH_2. The HUMO-LUMO gap narrows and the magnetic anisotropy energy decreases with the number of excitons. We have confirmed that some of the excitons carrying geometries are vibrationally stable. Progress on using calculated infrared frequencies and Raman frequencies for experimental confirmation will be reported.

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