Knowledge Bank

$MD2$ has been shown to be a van der Waals molecule with the two Mn atoms $(3d54s2)$ antiferromagnetically coupled $(J=-10cm-1)$ to form a $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\sigma g$ lowest $state.1Mn2$ can be formed in solid methane or cyclopropane at 12 K without reacting, and warming successively populates the higher $S=1,2,3,4,5$ spin states. These hydrocarbon matrices allowed higher temperatures to be reached than in rare-gas matrices with still resolvable spectra so that ESR transitions in $S=4$ and $S=5$ could be observed and analyzed. The derived g and D values corroborate the earlier application of the Judd-Owen theory.