Organometallic Frameworks from Isocyanide Ligands and M4S4-based Clusters

Metal-sulfur clusters have garnered significant attention for their delocalized electron density and structural tunability, which promotes their ability to serve as secondary building units (SBUs) in metal organic frameworks (MOFs), or porous coordination polymers, affording enhanced conductivity and redox properties.1,2,3 Described herein is an investigation into the feasibility of using M4S4 clusters as preformed nodes in conjunction with diisocyanide ligands as framework crosslinkers. We report a strategy of ligand exchange reactions with cubane-type clusters as precursors. Several aryl isocyanide ligands were screened in an effort to maintain the tetrahedral cubane-like cluster core geometry. The preparation of discrete clusters of unique nuclearities are described. In addition, ongoing efforts to prepare crystalline polymers initiated from these discrete clusters and ditopic (linker) isocyanides, under modulation by the monotopic ligands, will be presented. The clusters are characterized by single-crystal X-ray diffraction (scXRD), nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, and cyclic voltammetry (CV). The clusters and a proposed framework are studied via scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Ongoing collaborative efforts to further validate structures and properties by continuous rotation 3-dimensional electron diffraction (3D-ED), superconducting quantum interference device (SQUID) magnetic measurements, and conductivity measurements are also presented. This work was supported by the National Science Foundation (No. DMR-2045390).