Self-Assembly Rules of Dumbbell-Shaped Molecules and Their Effect on Morphology and Photophysical Behaviors of Micro/Nanocrystals

The dumbbell-shaped molecule is a crucial model in the organic optoelectronic field, but its molecular structure-morphology-property relationships are still unclear. In this work, we have identified the relationships relying on four dumbbell-shaped diarylfluorene derivatives through rationally modifying their two molecular segments: supramolecular bulky group (SBG) and core linkage (CL). By decreasing the bulky degree of SBG or lengthening the CL, a remarkable nanocrystal morphology transformation from 2D to 1D was observed. Morphology characterizations and supramolecular analysis show that the conversion of molecular packing mode from the slipped-layer motif to herringbone is responsible for the morphology transformation. Further disassembly investigation and calculation revealed the inner influence rules of SBG and CL segments on molecular arrangement and morphology. Finally, the proof-of-concept laser oscillators were fabricated based on the regular 2D sheet and 1D wire, and their different thresholds of 49.4 and 59.6 W/cm² were attributed to different molecular packing modes.