Coordination of hydrogen-bonding and π–π stacking induced elasticity and efficient optical-waveguiding in 4,7-bis(phenyl ethynyl)benzo[c][1,2,5] thiadiazole-based crystals

Abstract

Organic optical-waveguide crystals with a low optical loss coefficient and suitable elasticity are highly desired for flexible optoelectronic devices, in which achieving a balance between regular molecular orientation and elastic deformation remains a significant challenge. Herein, one-dimensional optical-waveguiding single crystals based on 4,7-bis((4-(2-methoxyethoxymethoxy)-3-nitrophenyl)ethynyl)benzo[c][1,2,5]thiadiazole (PEBTH-2N) were prepared through a facile self-assembly. These crystals exhibited a low optical loss coefficient of 0.013 dB μm⁻¹, polarized emission and excellent bendable capability. Single-crystal structural analysis and theoretical calculation revealed that the ortho-substituted nitro- and alkoxyl groups on the rigid PEBTH skeleton acted together to create a buffer region for molecular distance adaptation while maintaining a high degree of orientation in the crystals. This work provides a potential strategy for controlling the intermolecular interactions to construct flexible optical-waveguide crystals based on benzothiadiazole derivatives.