Effect of Substitution on the Hysteretic Phase Transition in a Bistable Phenalenyl-Based Neutral Radical Molecular Conductor

The ability to tune the physical properties of bistable organic functional materials by means of chemistry can facilitate their development for molecular electronic switching components. The butylamine-containing biphenalenyl boron neutral radical, Bu]₂B, crystalline compound has recently attracted significant attention by displaying a hysteretic phase transition accompanied by simultaneous bistability in magnetic, electrical, and optical properties close to room temperature. In this report, substitutional doping was applied to Bu]₂B by crystallizing solid solutions of bistable Bu]₂B and its non-radical-containing counterpart Bu]₂Be. With increasing doping degree, the hysteretic phase transition is gradually suppressed in terms of reducing the height, but conserves the width of the hysteresis loop as observed through magnetic susceptibility and electrical conductivity measurements. At the critical doping level of about 6 %, the abrupt transformation of the crystal structure to that of the pure Bu]₂Be crystal packing was observed, accompanied by a complete collapse of the hysteresis loop. Further study of the structure–properties relationships of bistable neutral radical conductors based on the Bu]₂B host can be conducted utilizing a variety of biphenalenyl-based molecular conductors.