A new fluorescent sensor L based on fluorene-naphthalene Schiff base for recognition of Al3+ and Cr3+

A new fluorescent probe 1-[(9H-fluoren-2-ylimino) methyl]-naphthalene (L) was synthesized which can be used to detect Al3+ and Cr3+ ions by fluorescence enhancement. The detection limits of L for Al3+ and Cr3+ ions were 8.87 x 10-8 and 6.31 x 10-8 M and the coordination constants were 3.25 x 103 and 2.09 x 103, respectively. Job ' s plot, 1H NMR titration and mass spectrometry experiments were conducted to discuss the coordination modes and the bonding ratios. The recognition mechanism was that during the recognition process, C--N group of L was oxidized into O--C-NH and was involved in coordination, which inhibited the C--N isomerization and resulted in enhanced fluorescence.