4-Azidocinnoline—Cinnoline-4-amine Pair as a New Fluorogenic and Fluorochromic Environment-Sensitive Probe

Abstract

A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for the amine was detected in polar solvents with the strongest fluorescence increase in water. The environment-sensitive fluorogenic properties of cinnoline-4-amine in water were explained as a combination of two types of fluorescence mechanisms: aggregation-induced emission (AIE) and excited state intermolecular proton transfer (ESPT). The suitability of an azide–amine pair as a fluorogenic probe was tested using a HepG2 hepatic cancer cell line with detection by fluorescent microscopy, flow cytometry, and HPLC analysis of cells lysates. The results obtained confirm the possibility of the transformation of the azide to amine in cells and the potential applicability of the discovered fluorogenic and fluorochromic probe for different analytical and biological applications in aqueous medium.

Thermo-Induced Fluorochromism in Two AIE Zinc Complexes: A Deep Insight into the Structure-Property Relationship

“…Due to their solid-state photoluminescent (PL) properties, many aggregation-induced emission materials (AIEgens) are FC active. MFC AIEgens change their packing structures in presence of external mechanical force [22], undergoing a variation in their PL pattern [1,12,[22][23][24][25][26]. In TFC AIEgens the variation of PL behaviour is caused by a thermal treatment inducing a molecular rearrangement [17,27,28].…”

“…In TFC AIEgens the variation of PL behaviour is caused by a thermal treatment inducing a molecular rearrangement [17,27,28]. Both MFC and TFC AIEgens have been used for advanced applications such as display devices, sensing, and optical data storage [17,24,[29][30][31][32][33][34][35][36][37][38]. Obviously, the structure-responsiveness relationship is critical for the prediction and understanding of AIEgens' fluorochromic response.…”