Preparation, structure and optical properties of TCNB-based charge-transfer cocrystals

Organic charge transfer cocrystals exhibit interesting properties due to their multi-components synergistic and collective effect. Herein, using 1,2,4,5-tetracyanobenzene (TCNB) as electron acceptor, carbazole (CARB), dibenzothiophene (DBZP) and dibenzofuran (DBZF) as electron donors, three charge transfer cocrystals of CARBTCNB, DBZP-TCNB and DBZF-TCNB were synthesized by solvent evaporation method and solvent-assisted grinding method. These cocrystals were constructed based on the pi-pi stacking interactions and C-H...N hydrogen bonds and confirmed by the SXRD analysis. The stacking modes are consistent with the model that predicted by molecular electrostatic potential analysis (ESP). The IGM and AIM analyses suggested that the pi-pi stacking and C-H...N hydrogen bonds are weak in nature. The purity and homogeneity of cocrystals and grinding products were verified by PXRD analysis. In addition, the IR, UV-vis absorption and luminescent properties were investigated, and the cocrystals and grinding products exhibited different behaviors from that of their precures. In short, this work not only reports the CT complexes synthesized by liquid- and solid- strategies, but also provides an in-depth understanding of the spectral changes caused by the CT interactions.