The roles of heteroatoms and substituents on the molecular packing motif from herringbone to π-stacking: A theoretical study on electronic structures and intermolecular interaction of pentacene derivatives

Molecular stacking motifs in solid play a pivotal role on the charge transport properties of materials. The relationship between molecular structure and packing motifs in solid remains challenging. In the present work, the single crystal structures of PEN-O, PEN-N, PEN-CF3 and TPDO were predicted by evolutionary algorithm using the USPEX program. The stacking motifs, the electronic structures and the stabilities of pentacene (PEN) derivatives are systematically investigated by employing density functional theory. Our study expounded how the introduction of heteroatoms (oxygen-atom and nitrogen-atom) and substituent (trifluoromethyl) adjust their electronic structure effectively to improve the capability of carrier injection. Hirshfeld surface analysis was performed for the intermolecular close contact points to rationalize the molecular stacking patterns in solid. In addition, electrostatic potential and energy decomposition by symmetry adapted perturbation theory are analyzed to reveal the effects of heteroatoms and substituents on charge distribution and noncovalent interactions. Through introducing heteroatoms and substituents into PEN, the charge redistribution leads to non-uniform electrostatic potentials of conjugated molecular skeleton, which results in the change of the stacking patterns from herringbone to pi-stacking. Furthermore, incorporating oxygen-atom or nitrogen-atom into PEN decreases dispersion energies, while modifying PEN with trifluoromethyl increases the dispersion energy. However, both of them lead to the decrease of the electrostatic and exchange-repulsion energy.