Effect of structural variation on AIE behavior: A case study of salicylaldehyde-naphthaldehyde-azine based of meta...

AIE-ESIPT-active azine-based fluorophores offer notable benefits and diverse applications. Recent research has emphasized the exceptional properties of meta-fluorophores, such as strong charge transfer characteristics, emissions in longer wavelength regions, and large Stokes shifts. Despite their potential, investigations into the impact of meta substitution, particularly in AIE-ESIPT-active fluorophores, are still in their early stages. This work presents a case study of salicylaldehyde-naphthaldehyde-azine-based fluorophores (p-NK and m-NK) compared to our previous research findings (p-BK and m-BK). Similar to earlier research, m-NK exhibited enhanced charge transfer character, a red-shifted emission, and a longer excited-state lifetime than p-NK. However, a notable change in the AIE behavior of m-NK is attributed to the structural variation in the azine skeleton. Both fluorophores consistently demonstrate the same high selectivity and remarkable sensitivity toward copper ions, showing no interference from other metal ions. Furthermore, their potential for practical application in copper ion detection was tested under diverse conditions, including real-world samples such as water, biological fluids (urine), and living cells, to assess their applicability to the real world. In conclusion, this study presents the potential of previously identified meta-fluorophores, paving the way for research to develop and synthesize novel AIE-active fluorophores with tailored aggregation behavior and emission wavelengths.