Emission enhancement and chromism in a salen-based gel system

A new salicylideneaniline-based organogelator has been synthesized, and it can gelatinize organic solvents, including cyclohexane, toluene, benzene, and some mixed solvents. SEM images show that it has self-assembled into 1-D nanofibers, which further cross-link to form 3-D network. On the basis of the results of small-angle XRD and the optimized molecular length by semiempirical quantum calculations, the gelators are supposed to pack into a unimolecular lamellar structure with a period of 3.01 nm. Significantly, reversible chromism is realized with respect of the tautomerism between the NH and OH forms during the sol-gel freezing repetition. Furthermore, the gel can emit intense green light, and the fluorescent quantum yield of the gel is approximately 600 times higher than that of the solution. The aggregation-induced emission enhancement is ascribed to the formation of J aggregation and the inhibition of intramolecular rotation in the gel state.