Development of Rhodamine 6G-Based Fluorescent Chemosensors for Al3+-Ion Detection: Effect of Ring Strain and Substituent in Enhancing Its Sensing Performance

Four rhodamine 6G-based chemosensors (H(3)L1-H(3)L4) are designed for selective detection of Al3+ ion. They are characterized using various spectroscopic techniques and X-ray crystallography. All absorption and emission spectral studies have been performed in 10 mM N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (HEPES) buffer solution at pH 7.4 in H2O/MeOH (9:1, v/v) at 25 degrees C. In absorption spectra, chemosensors exhibit an intense band around 530 nm in the presence of Al3+ ion. Chemosensors (H(3)L1-H(3)L4) are nonfluorescent when excited around 490 nm. The presence of Al3+ ion enhances the emission intensity (555 nm) many times. The formation of complexes 1-4 is established with the aid of different spectroscopic techniques. The limit of detection value obtained in the nanomolar range confirms the high sensitivity of the probes toward Al3+ ion. It has been observed that the presence of aliphatic spacers in the diamine part and different halogen substituents in the salicylaldehyde part strongly influences the selectivity of the chemosensors toward Al3+ ion. The propensity of the chemosensors to identify intracellular Al3+ ions in triple-negative human breast cancer cell line MDA-MB-468 by fluorescence imaging is also examined in this study.