In-situ high pressure crystallization of a solvated form of DPA

9,10-diphenylanthracene (DPA) has recently attracted attention as an organic semiconductor with high electron and hole mobilities, probabily resulting from an effective intermolecular linking between successive layers inside the crystal, via the anthracene-backbone-phenyl-groups. DPA crystallizes in space group C2/c (a = 10.69; b = 13.58; c = 12.29 Å; β = 90.6°) with the two phenyl groups almost orthogonal to the anthracene backbone. No other polymorphic crystal structure has been reported in literature, although some solvated forms of the molecule are known. In this work we have obtained a particularly interesting novel solvated form by means of in-situ high-pressure crystallization of a solution of DPA in 1,1,2,2-tetrachloroethane. While slow evaporation of the saturated solution at ambient pressure lead to the formation of the C2/c polymorph, loading the same solution into a diamond-anvil cell (DAC) and increasing the pressure to 5 kbar induced the formation of a solvated form crystallizing in space group P21/c (a = 8.79; b = 12.03; c = 13.82 Å; β = 104.96°). In this new structure, the torsion angle between the two phenyl groups and the anthracene backbone is even closer to 90° and the intermolecular interaction linking between successive layers of DPA molecules is no longer present. This feature is replaced by a three dimensional network of CH-π interactions that link together para-hydrogens on the phenyl rings of each molecule with the external anthracene ring of an adjacent one, resulting in the formation of hosting channels extending in the direction of the a-axis, occupied by the solvent molecules. Although it has not been possible to recover the crystal at ambient pressure, the analisys of this solvate form could contribute to enhance our knowledge of the intermolecular interactions that are responsible for the semiconductive properties of DPA.