γ-Herringbone Polymorph of 6,13-Bis(trimethylsilylethynyl)pentacene: A Potential Material for Enhanced Hole Mobility.

The introduction of the trialkylsilylethynyl group to the acene core is known to predominantly transform the herringbone structure of pentacene to a slip-stacked packing. However, herein, the occurrence of an unforeseen polymorph of 6,13-bis(trimethylsilylethynyl)pentacene (TMS-pentacene), with an atypical γ-herringbone packing arrangement, is reported. Intermolecular noncovalent interactions in the γ-herringbone polymorph are determined from Hirshfeld surface and quantum theory of atoms-in-molecules (QTAIM) analyses. Furthermore, a comparative truncated symmetry-adapted perturbation theory (SAPT(0)) energy decomposition analysis discloses the role of exchange repulsions that govern molecular packing in the γ-herringbone polymorph. Moreover, the computationally predicted electronic coupling and anisotropic mobility reveal the possibility of enhanced hole transport (μh =3.7 cm2  V-1  s-1 ) in the γ-herringbone polymorph, in contrast to the reported polymorph with a hole mobility of μh =0.1 cm2  V-1  s-1 .