V-shaped oxydiphthalimides: side-chain engineering regulates crystallisation-induced emission enhancement

Tuning the luminescence properties of solid state materials by controlling the molecular packing in the crystal has played an important role in designing new functional materials. A series of five V-shaped oxydiphthalimides (ODPs) were synthesised. Side-chain engineering has been successfully utilized to systematically tune their luminescence properties in the crystalline state by introducing sterically bulky side-chains at the imidic nitrogen. Fluorescence spectroscopy and single crystal X-ray analyses disclose the effect of conformational twisting and bulkiness of imidic substituents on crystallisation-induced emission enhancement (CIEE). Detailed analysis revealed that the CIEE factor of ODPs shows a linear dependence on the percentage volume of the side-chain.