Bis(triarylmethylium)‐type Macrocyclic Dications: Mechanochromic Emission Extending to the Red Region

Abstract

AbstractMacrocyclic dications22+composed of two triarylmethylium units were designed and synthesized. In contrast to the reference monocations1+, macrocyclic dications22+exhibited mechanochromic emission extending to the red region (−900 nm), since the luminescence color in a solid state can reversibly change due to their constrained structures granted by alkylene linkers and the choice of a proper counterion. X‐ray diffraction and spectroscopic analyses revealed that such mechanochromic behavior was induced by the crystal‐to‐amorphous transition. A change in the intermolecular interaction of macrocyclic dications22+would be the key to realizing a change in the emission pattern, since the color of the molecules did not change by applying mechanical stimuli. These findings may suggest a design strategy for creating a variety of stimuli‐responsive materials, especially for carbocation‐based fluorescent materials.