Sprachmann, J.; Wachsmuth, T.; Bhosale, M.; Burmeister, D.; Smales, G.J.; Schmidt, M.; Kochovski, Z.; Grabicki, N.; Wessling, R.; List-Kratochvil, E.J.W.; Esser, B.; Dumele, O.: Antiaromatic Covalent Organic Frameworks Based on Dibenzopentalenes. Journal of the American Chemical Society 145 (2022), p. 2840–2851
10.1021/jacs.2c10501
Abstract:
Despite their inherent instability, 4n π systems have recently received significant attention due to their unique optical and electronic properties. In dibenzopentalene (DBP), benzanellation stabilizes the highly antiaromatic pentalene core, without compromising its amphoteric redox behavior or small HOMO–LUMO energy gap. However, incorporating such molecules in organic devices as discrete small molecules or amorphous polymers can limit the performance (e.g., due to solubility in the battery electrolyte solution or low internal surface area). Covalent organic frameworks (COFs), on the contrary, are highly ordered, porous, and crystalline materials that can provide a platform to align molecules with specific properties in a well-defined, ordered environment. We synthesized the first antiaromatic framework materials and obtained a series of three highly crystalline and porous COFs based on DBP. Potential applications of such antiaromatic bulk materials were explored: COF films show a conductivity of 4 × 10–8 S cm–1 upon doping and exhibit photoconductivity upon irradiation with visible light. Application as positive electrode materials in Li-organic batteries demonstrates a significant enhancement of performance when the antiaromaticity of the DBP unit in the COF is exploited in its redox activity with a discharge capacity of 26 mA h g–1 at a potential of 3.9 V vs. Li/Li+. This work showcases antiaromaticity as a new design principle for functional framework materials.