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

Tuning of Molecular Electrostatic Potential Enables Efficient Charge Transport in Crystalline Azaacenes: A Computational Study

“…Note that the introduction of EWGs can sometimes result in the opposite structural changes, as extensive fluorination can induce the crossover to a herringbone structure from a π-stacking one [19,21,22]. The insertion of a heteroatom directly in the conjugated core, e.g., the substitution of CH with N (N-substitution), can be another way of tuning the crystal structure, as this substitution also weakens edge-to-face interactions and facilitates edge-to-edge and face-to-face interactions [13,[23][24][25]. However, this molecular structure modification is much less common in the design of OSs as compared to fluorination and cyano-substitution, and its effect is worth a detailed investigation.…”

“…A convenient playground for studying the impact of N-substitution on the crystal structure and properties is the series of oligoacenes-one of the most studied classes of OSs. Accordingly, a comparison of the oligoacenes and their N-substituted counterparts-azaacenes-was performed in several studies [13,[23][24][25]. It was observed that, while oligoacenes favor herringbone crystal packing [26], their N-substituted counterparts can show a π-stacking packing motif [23][24][25]27].…”

“…Accordingly, a comparison of the oligoacenes and their N-substituted counterparts-azaacenes-was performed in several studies [13,[23][24][25]. It was observed that, while oligoacenes favor herringbone crystal packing [26], their N-substituted counterparts can show a π-stacking packing motif [23][24][25]27]. In line with the reasoning provided above, changes in the crystal structure were attributed to the changes in the electrostatic potentials of the oligoacene molecules with N-substitution and the emergence of CH• • • N weak hydrogen bonds [23,24].…”

“…It was observed that, while oligoacenes favor herringbone crystal packing [26], their N-substituted counterparts can show a π-stacking packing motif [23][24][25]27]. In line with the reasoning provided above, changes in the crystal structure were attributed to the changes in the electrostatic potentials of the oligoacene molecules with N-substitution and the emergence of CH• • • N weak hydrogen bonds [23,24]. Nevertheless, a systematic study of the effect of N-substitution on the crystal packing of various oligoacenes is lacking.…”

“…The role of the number and position of the nitrogen heteroatoms in the mentioned π-conjugated cores is systematically analyzed. Only azaacenes (without side groups) that were successfully synthesized, and for which the crystal structure is known, are considered; this distinguishes our study from recent reports where predicted crystal structures were used [23,24] or substituted azaacenes were addressed [31]. Furthermore, the molecular packing and charge transport in the crystals of azaacenes with four nitrogen atoms, which have not been addressed theoretically before, are considered.…”