Benzoselenadiazole Containing Donor–Acceptor–Donor Small Molecules: Nonbonding Interactions, Packing Patterns, and Optoelectronic Properties

Herein, we describe the fine-tuning of intermolecular Se···N interaction in benzoselenadiazole (BDS) derivatives to form head-to-head dimers in the solid state. The structures and photophysical properties of phenyl-, thiophene-, and selenophene-capped BDS (1–3, respectively) are studied here. Because of the presence of the strong intramolecular Se···N interaction, selenophene-capped BDS 3 showed syn arrangement of two capped selenophene rings, whereas two thiophene rings in 2 showed an anti orientation. Compounds 1 and 2 showed the tendency to form head-to-head dimers in the solid state through the intermolecular Se···N interactions. In contrast to compounds 1 and 2, compound 3 does not form a dimer in the solid state and, instead, shows strong intramolecular Se···N interactions. The tendency to form dimers largely depends on the nonbonding interactions and the steric effect of capped rings.