Fluorescent sensor of fluorene derivatives having phosphonic acid as a fluorogenic ionophore: synthesis and static quenched properties for Fe(III)

A series of novel fluorene derivatives containing -PO(OH)2 (1, 2), -HS (3), and -N+ (CH3)3 (4) were synthesized and only phosphonic-functionalized fluorene derivatives can detect Fe3+ with high selectivity over other metal ions. The fluorescence quenching of 1 and 2 with titration Fe3+ in water-DMF solution fits the Perrin model of static quenching. Spectral analysis showed that Fe3+ bound with fluorene-based chemosensor through the O-atoms at the phosphonic group to form nonfluorescent complexes. The binding ratio was estimated by the Job plot and the trace levels of iron in samples were successfully monitored.