Protonation-induced change in the conformation, crystal structure and property of triarylmethyl carbocation radical

Highlights: ⿢Novel triarylmethyl carbocation radicals were facilely prepared. ⿢The protonation triggered conformational change. ⿢Conformational change induced the change in crystal structures and properties. ⿢Various phosphorescent properties and magnetic susceptibility data. We report a new triarylmethyl carbocation radical which was easily synthesized via ⿿one-pot⿿ approach. Interestingly, this ⿿cis⿿ triarylmethyl carbocation radical converted to the ⿿trans⿿ one upon protonation. Such an obviously conformational change is triggered by the intermolecular hydrogen bond interaction involving one exocyclic ⿿keto⿿ oxygen atom and the protonated pyridinium nitrogen atom. Two triarylmethyl carbocation radical crystals were characterized by the elemental analysis and single crystal X-ray diffraction. A change in conformation also brings about change in crystal structure, phosphorescence and magnetic susceptibility properties.