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Structures and photophysical properties of two luminescent bipyridine compounds: 2',6'-difluoro-6-[3-(pyridin-2-yloxy)phenyl]-2,3'-bipyridine and 2',6'-dimethoxy-6-[3-(pyridin-2-yloxy)phenyl]-2,3'-bipyridine.

The title compounds, C21H13F2N3O (1) and C23H19N3O3 (2), have been synthesized by typical cross-coupling reactions. Both compounds have been characterized by single-crystal X-ray diffraction. Bipyridine 1 exhibits a fully extended structure in which the terminal pyridine rings are oriented away from each other, while bipyridine 2 displays a bent structure in which terminal pyridine rings are oriented in the same direction. Several intermolecular interactions lead to the formation of two- and three-dimensional supramolecular networks in the crystal structures of 1 and 2, respectively. Compound 1 bears fluorine substituents and emits a strong fluorescence with λmax = 325 nm, while methoxy-substituted compound 2 displays red-shifted emissions with λmax = 366 nm. The emissions observed in both compounds originate from phenyl- and 2,3'-bipyridine-based π-π* transitions, according to theoretical calculations. Both compounds have high triplet energies (T1) ranging from 2.64 to 2.65 eV, which makes them potential host materials in organic light-emitting diodes (OLEDs).