Improvement of Solid‐State Excimer Emission of the Aryl–Ethynyl‐<i>o</i>‐Carborane Skeleton by Acridine Introduction

Abstract

We report highly‐efficient and solid‐state excimer emission based on the acridine– o ‐carborane dyad possessing the ethynyl spacer. The previous pyrene‐modified o ‐carborane showed excimer emission only at 77 K in the crystalline state, meanwhile, the current acridine‐modified molecule presented excimer emission with high efficiency ( Φ PL = 0.23) in the crystalline state at room temperature. From single‐crystal X‐ray crystallography, it was indicated that two acridine moieties were stacked and the third acridine molecule was out of alignment. Such a packing mode could restrict exciton splitting over the columnar packing structure. Moreover, molecular interactions through the nitrogen atom in the acridine moiety and the hydrogen atom in the o ‐carborane unit contribute to suppression of molecular motions. As a consequence, an improved emission efficiency was obtained. This study demonstrates that the ethynyl– o ‐carborane skeleton should work as the excimer‐inducible component in the solid state.