Antiaromatic Covalent Organic Frameworks Based on Dibenzopentalenes

Despite their inherent instability, 4n pi-systems have recently received significant attention due to their unique optical and electronic properties. In dibenzopentalene, 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 ill-defined amorphous polymers can limit the performance (e.g. due to solubility in the electrolyte solution or low internal surface area). Covalent organic frameworks, 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 covalent organic frameworks based on dibenzopentalene. 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. Investigations as battery electrode materials demonstrate their ambipolar nature and the ability to store both anions and Li ions with enhanced charge storage capabilities compared to an aromatic COF or the conductive carbon material. This work showcases antiaromaticity as a new design principle for functional framework materials

Anomalous Subdiffusion Is a Measure for Cytoplasmic Crowding in Living Cells

Macromolecular crowding dramatically affects cellular processes such as protein folding and assembly, regulation of metabolic pathways, and condensation of DNA. Despite increased attention, we still lack a definition for how crowded a heterogeneous environment is at the molecular scale and how this manifests in basic physical phenomena like diffusion. Here, we show by means of fluorescence correlation spectroscopy and computer simulations that crowding manifests itself through the emergence of anomalous subdiffusion of cytoplasmic macromolecules. In other words, the mean square displacement of a protein will grow less than linear in time and the degree of this anomality depends on the size and conformation of the traced particle and on the total protein concentration of the solution. We therefore propose that the anomality of the diffusion can be used as a quantifiable measure for the crowdedness of the cytoplasm at the molecular scale