Quencher displacement strategy for recognition of trivalent cations through 'turn-on' fluorescence signaling of an amino acid hybrid

An in situ generated anthracene based hybrid amino acid 1-Cu2+ complex has been utilized efficiently as a light-up probe to detect biologically/environmentally important trivalent metal ions Fe3+/Cr3+/Al3+ through turn-on fluorescence signaling. Whereas the amino acid derivative 1 showed a poor selectivity toward various metal ions, the 1-Cu2+ ensemble showed a high selectivity toward trivalent cations. The enhancement in fluorescent intensity of 1-Cu2+ was due to the displacement of Cu2+ from 1-Cu2+ by Fe3+/Cr3+/Al3+. Interestingly, the displacement of a paramagnetic ion (Cu2+) by other paramagnetic ions (Fe3+/Cr3+) resulted in an increase in fluorescence intensity by many folds. The selectivity was established in the presence of a large number of different metal ions using various spectroscopic techniques. This 1-Cu2+ ensemble was also found to be a selective sensor for phosphate anion.