Asymmetric Molecular Conformation of Steric Terfluorene toward Constructing Polyhedral Microcrystals for Deep-Blue Lasers

Molecular conformation is crucial for precisely controlling photophysical processing and self-assembly behavior of organic conjugated semiconductors for optoelectronic applications. Herein, we obtained a novel asymmetric molecular conformation of steric terfluorene with torsion angles of −172 and 44° to enable its molecules to self-assemble into a polyhedral microcrystal for deep-blue lasers. Interestingly, significantly different from previous quasi-symmetrical ones, novel asymmetric secondary interactions, including C–H···π and O···H–C hydrogen bonds, are easily observed in our novel crystalline structure and enable DOSFX-SFX molecules to self-organize into an octahedral microcrystal, which is an excellent optical microcavity for organic lasers. Meanwhile, a supramolecular steric encapsulation layer can be induced by large hindrance of SFX nanogroups and simultaneously effectively inhibited intermolecular π–π interactions, allowing for intramolecular photophysical behavior in crystal states. With an intermediated and asymmetric conformation, our DOSFX-SFX molecules exhibited a longer effective conjugated length with a red-shifted 0–1 emission peak at 430 nm than the controlled ones (417 nm) with a larger torsional adjacent angle but a shorter length than the quasi-planar conformational ones (445 nm), confirming the key role of molecular conformation in controlling photophysical behavior. Finally, DOSFX-SFX octahedron-based low-threshold microlasers are also constructed with a 0–1 band emission peak at 417 ± 2 nm, which suggested intramolecular photophysical behavior in crystal states. Our work supported an assumption that molecular conformation is a key factor to control a material’s properties and self-assembly behaviors