Linker Aromaticity Reduces Band Dispersion in 2D Conductive Metal-Organic Frameworks

All 2D electrically conductive metal-organic frameworks (MOFs) are constructed from hexasubstituted aromatics that oxidize during self-assembly. Since electrical conduction is thought to occur through the ligand pi-system, but aromaticity itself results in stabilized pi-electrons, the delocalization of ligand wavefunctions should be inversely related to the ligand pi-stability. That is, aromatic pi-electrons should prefer to localize on a single linker rather than delocalize to form a curved band in the MOF. Here, we use a combination of NICS-xy scans and bulk electronic band structure calculations to show that the extent of residual aromaticity in the oxidized linker is a good predictor for electronic localization in the resultant MOF. Thus, ligands that feature antiaromatic pi-systems in the oxidation state found within the MOF should yield increased band curvature, a target parameter that affects charge mobility in high performing electrical conductors.