Chemical Oxidation of Chrysene: A Structural and Theoretical Description of a Mixed-Valent Trimeric Radical Cation

Chemical oxidation of chrysene with GaCl₃ affords a trimeric chrysene radical dication, [(C₁₈H₁₂)₃]²⁺, crystallized with two Ga₂Cl₇ ^- anions, as revealed by single crystal X-ray diffraction analysis. In the crystal structure, 1D π-stacked columns of chrysene with interplanar contacts averaged at 3.303(3) Å are separated by Ga₂Cl₇ ^- anions. Computational studies reveal that the positive charge is concentrated largely on the terminal chrysene units with charges of +0.84 and +0.80, while the center chrysene has a comparatively lower charge of +0.36. This charge distribution is corroborated with structural features of the trimer, as the terminal chrysene molecules exhibit a more pronounced core deformation. Taking the neutral trimer as a reference, much weaker interactions are observed in the title chrysene trimer bearing a +2 charge, suggesting the presence of substantial electrostatic repulsion.