Two dimensional directed π–π interactions in a linear shaped bi-1,3,4-oxadiazole derivative to achieve organic single crystal with highly polarized fluorescence and amplified spontaneous emissions

Abstract

We report the role of the molecular structure and molecular interactions of linear shaped bi-1,3,4-oxadiazole derivatives (BOXD-n) on their self-assembly behaviors and optical properties. The terminal chains of BOXD-n (n = 1, 4) play an important role in molecular self-assembling and their optical properties. High fluorescence efficiency (Φ_F = 56%) was observed in BOXD-4 single crystal, while relatively low fluorescence efficiency (Φ_F = 21%) was observed in BOXD-1 single crystal. Highly polarized fluorescence (I_max/I_min of 23) and deep blue ASE (λ = 403 nm, threshold of about 20 kW cm⁻²) were observed in BOXD-4 single crystal, in which molecules uniaxially J-type aggregate through both face-to-face and edge-to-edge π–π interactions between 1,3,4-oxadiazole rings and phenyl rings. No polarized fluorescence or ASE phenomenon was observed in BOXD-4 vacuum evaporated films.