Simple salicylaldimine-functionalized dipodal bis Schiff base chromogenic and fluorogenic chemosensors for selective and sensitive detection of Al3+ and Cr3+

Two salicylaldimine-functionalized dipodal bis Schiff base low cost fluorescent colorimetric chemosensors L1 (bis([4-(2-hydroxy-3-methoxybenzyl-ideneamino)phenyl]ether) and L2 (di[(4-phenylimino)4-diethylsalicyl-al-dehyde]ether) have been designed and synthesized. These sensors could simultaneously detect two biologically important metal ions (AI(3+) and Cr3+) by change in both absorption and fluorescence intensity in CH3CN-H2O (1/1, v/v) solvent mixture at physiological pH. The jobs plot analyses indicate the 2:2 binding stereochemistry for Al3+ and Cr3+ ions with both the probes Ll and L2, which were further been confirmed by H-1 NMR and ESI-MS studies. The binding constant values for Ll were found to be 2.35 x 10(5)M(-1) for Al3+ and 1.26 x 10(5)M(-1) for Cr3+ and in case of L2 these values are 1.46 x 10 5 M-1 for Al3+ and 3.0 x 10 5 M-1 for Cr3+. The detections limits of the sensor LI, for Al3+ (1.73 x 10(-7)M) and Cr3+ (1.12 x 10(-7)M) and of the sensor L2, for Al3+ (4.34 x 10(-7)M) and Cr3+ (7.73 x 10(-7)M) are far below than the limit set by the World Health Organization (WHO) for drinking water. Moreover, visible colorimetric test kits and real samples for rapid detection of Al3+ and Cr3+ could be successively applied for all practical purposes, indicating their potential use in environmental samples.