Cove‐Edged Hexa‐ peri ‐hexabenzo‐bis‐ peri ‐octacene: Molecular Conformations and Amplified Spontaneous Emission

Abstract

The bottom‐up synthesis of an unprecedentedly large cove‐edged nanographene, hexa‐peri‐hexabenzo‐bis‐peri‐octacene ( HBPO ), is reported in this work. Chiral high‐performance liquid chromatography and density functional theory (DFT) calculations revealed multiple conformations in solution. Two different molecular conformations, “waggling” and “butterfly”, were found in crystals by X‐ray crystallography, and the selectivity of conformations could be tuned by solvents. The optoelectronic properties of HBPO were investigated by UV/Vis absorption and fluorescence spectroscopies, cyclic voltammetry, and DFT calculations. The contorted geometry and branched alkyl groups suppress the aggregation of HBPO in solution, leading to a high fluorescence quantum yield of 79 %. The optical‐gain properties were explored through transient absorption and amplified spontaneous emission spectroscopies, which enrich the choices of edge structures for potential applications in laser cavities.