Structural Characteristics of a Partially Planarized Triarylmethyl Cation with Unsymmetrical Push-Pull Structure

We report the physical properties of a new class of triarylmethyl-based carbocations containing both an electron-donating diphenyl ether moiety and an electron-accepting carbonyl group with a helical plane framework. Their unique packing patterns were clarified by X-ray crystallographic analysis, which depend on the counter anions to influence their photophysical properties in the solid states. Notably, the interactions between π-cation species and planar anion species lead to a unique panchromatic property, accompanying a near-infrared absorption with a λ_onset value of 1030 nm, which can be assigned to intermolecular charge transfer transition. We found that the π-cation species with planar anion formed cation dimers, being stacked in opposite directions. The two cation molecules are flanked by two anions on both the top and bottom side. Pair interaction energy decomposition analysis (PIEDA) calculations imply that the origins of the unique packing patterns of the π-cations originate from the electrostatic forces of four neighbouring π-anion species.