Topological Transformation of π‐Conjugated Molecules Reduces Resistance to Crystallization

Two electronically delocalized molecules were designed as models to understand how molecular shape impacts the tradeoff between solubility and crystallization tendencies in molecular semiconductors. The more soluble compound TT contains a non‐planar bithiophene central fragment, whereas CT has a planar cyclopentadithiophene unit. Calorimetry studies show that CT can crystallize more easily than TT . However, absorption spectroscopy shows that the initially amorphous TT film can eventually form crystals in which the molecular shape is significantly more planar. Two thermally reversible polymorphs for TT were observed by XRD and grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) measurements. These findings are relevant within the context of designing soft semiconductors that exhibit high solubility and a tendency to provide stable organized structures with desirable electronic properties.     

Solvent‐Induced Control over Breathing Behavior in Flexible Metal–Organic Frameworks for Natural‐Gas Delivery

Finding appropriate stimuli for controlling the breathing behavior of flexible metal–organic frameworks (MOFs) is highly challenging. Herein, we report the solvent‐induced changes in the particle size and stability of different breathing phases of the MIL‐53 series, a group of flexible MOFs. A water/dimethylformamide (DMF) ratio is tuned to synthesize members of the MIL‐53 series which have different behaviors. The breathing is explored by high‐pressure methane sorption tests. Increasing DMF concentration decreases MOF particle size and increases the stability of the porous phases, boosting the 5.8–65 bar sorption difference of methane, which is required for natural‐gas delivery.