Single sensors for multiple analytes employing fluorometric differentiation for Cr3+ and Al3+ in semi-aqueous medium with bio-activity and theoretical aspects

The structurally characterized (through single crystal X-ray diffraction) Schiff base ligand N,N-bis(4-methoxy-salicylaldehyde)azine (H(2)SALNN) exhibits poor fluorescence in the excited state, due to rotational (cis/trans) isomerization along the azomethine group. However, in the presence of Cr3+ and Al3+ the isomerization is blocked due to coordination with the metal ions exhibiting turn-on fluorescence. The fluorescence enhancement for Al3+ and Cr3+ at two distinct wavelengths shows much difference of the wavelengths (I = 63 nm). Thus, the selective turn-on fluorescence behaviour of H(2)SALNN for Cr3+ and Al3+ is based on the blocking effect of C?N isomerization and chelation-enhanced fluorescence (CHEF). The coordination modes of the complexes were investigated by spectroscopic and computational studies.