Deuteron NMR of a manganese-ion cluster nanomagnet

The temperature dependence of deuteron NMR spectra of the fully deuterated manganese ion cluster nanomagnet $\rm Mn_{12}O_{12}$-acetate has been measured. Two sets of deuteron peaks have been observed which both shift towards lower fields with decreasing temperature. The strongly shifted peak is associated with the deuterons of the four $\rm D_2O$ molecules which are directly attached to the Mn core. The less shifted peak is due to the $-\rm CD_3$ deuterons, which are three bonds away from the oxygen that is attached to Mn ions, as well as to the solvated $\rm D_2O$ and $\rm CD_3COOD$ molecules. The results imply that the unpaired spin density extends over the whole molecular cluster rather than being concentrated at the Mn ions.