On Mechanochemical Dimerization of Anthracene. Different Possible Reaction Pathways

Calculations of the anthracene crystal structure, 10% isotropic compression of the anthracene crystal and its two dimers linked not through the central atoms of central rings are performed in the density functional theory approximation. Linear lattice parameters a, b, c, interatomic distances, and bond angles coincide with those determined by single crystal X-ray diffraction and previously calculated for an isolated anthracene molecule. The parameter γ is different by 12⪤g, which is due to a weak dependence of the lattice energy on γ (the energy of only a few kcal per mole is required to turn the lattice at this angle). The calculated lattice energy (15 kcal/mol) is close to the enthalpy of sublimation. Dimers of another configuration than those linked through the central atoms of central rings are less energetically favorable. The formation of dimers at high pressure and shear deformation of “sandwiches” composed of anthracene molecules located above each other is shown, and a two-step dimerization scheme is proposed.