Metal-Organic Frameworks (MOFs) of a Cubic Metal Cluster with Multicentered Mn-I-Mn-I Bonds

摘要

MOFs with both multicentered metal-metal bonds and low-oxidation-state (LOS) metal ions have been underexplored hitherto. Here we report the first cubic [Mn-8(I)] cluster-based MOF (1) with multicentered Mn-I-Mn-I bonds and + 1 oxidation state of manganese (Mn-I or Mn(I)), as is supported by single-crystal structure determination, XPS analyses, and quantum chemical studies. Compound 1 possesses the shortest Mn-I-Mn-I bond of 2.372 angstrom. Theoretical studies with density functional theory (DFT) reveal extensive electron delocalization over the [Mn-8(I)] cube. The 48 electrons in the [Mn-8(I)] cube fully occupy half of the 3d-based and the lowest 4s-based bonding orbitals, with six electrons lying at the nonbonding 3d-orbitals. This bonding feature renders so-called cubic aromaticity. Magnetic properties measurements show that 1 is an antiferromagnet. This work is expected to inspire further investigation of cubic metal-metal bonding, MOF materials with LOS metals, and metalloaromatic theory.