Role of Intermolecular Interactions in Molecular Packing of Alkoxy-Substituted Bis-1,3,4-oxadiazole Derivatives

The molecular packing, intermolecular interactions, and electron-transporting and photophysical properties of a series symmetrical alkoxy-substituted bis-1,3,4-oxadiazole derivatives (BOXD-o-OCH3, BOXD-m-OCH3, BOXD-D1, and BOXD-T1) are carefully investigated through a combination of experimental techniques and theoretical calculations here. The single-crystal structure analysis reveals that all these single crystals exhibit similar layer structures, while their molecular structures, displacement of the nearest adjacent molecules in π-stacking, and molecular packing modes are effectively tuned by changing the positions, amounts, or lengths of alkoxy groups in these compounds. Careful analysis of intermolecular interactions demonstrated that π–π intermolecular interactions are the main forces in the formation of single crystal and that C–H···O intermolecular interactions have a non-negligible contribution in determining the distinguished packing modes of these single crystals. BOXD-o-OCH3-α crystal exhibit a maximum calculated electron mobilities value (5.2 cm2V–1S–1) among these selected crystals. The absorption and emission maxima of these single crystals exhibit different redshifts. In addition, these single crystals also exhibit high fluorescence quantum efficiency. Our investigations would not only provide an effective way to tuning crystal packing but also guide the design of materials with excellent performance in a device.