Difluoromethoxyl bridged substituted 2-cyano-pyrrole based pure organic luminescent liquid crystals towards white light emitting single-molecule

A series of new luminescent liquid crystals (LLCs) comprised of difluoromethoxy and substituted 2-cyano-pyrrole (CN-Py) bridge with the molecular rigid core were synthesised. Their emission colours could be adjusted facilely and reversibly in a non-invasive manner by simply changing the excitation wavelength at room temperature. A simple and practical approach has been developed to avoid the use of hazardous and highly toxic elemental bromine to achieve a green and environmentally friendly synthesis pathway for difluoromethoxy-bridged liquid crystals. Notably, excitation-dependent multicolour luminescence has been realised in a single molecule of 5CC-CF2O-2Br-CN based on pure organic difluoromethoxy bridged liquid crystal, whose emission colours changes from yellow to blue with a blue shift of excitation wavelength. Interestingly, the CIE coordinates (0.29,0.33) of 5CC-CF2O-2Br-CN is very close to the white light coordinates (0.33, 0.33) under excitation at a wavelength of 335 nm. Therefore, 5CC-CF2O-2Br-CN can be a candidate of promising white light emitting luminescent liquid crystal. This protocol offers efficient access to single-molecule liquid crystal material with white light emission.