Million-Fold Electrical Conductivity Enhancement in Fe2(DEBDC) versus Mn2(DEBDC) (E = S, O)

Reaction of FeCl2 and H4­DSBDC (2,5-disulfhydryl­benzene-1,4-dicarb­oxylic acid) leads to the formation of Fe2­(DSBDC), an analogue of M2­(DOBDC) (MOF-74, DOBDC4– = 2,5-dihydroxy­benzene-1,4-dicarb­oxylate). The bulk electrical conductivity values of both Fe2­(DSBDC) and Fe2­(DOBDC) are ∼6 orders of magnitude higher than those of the Mn2+ analogues, Mn2­(DEBDC) (E = O, S). Because the metals are of the same formal oxidation state, the increase in conductivity is attributed to the loosely bound Fe2+ β-spin electron. These results provide important insight for the rational design of conductive metal–organic frameworks, highlighting in particular the advantages of iron for synthesizing such materials.