A tripodal imine-derived Fe(III) complex for the fluorescence recognition of Mg(II) via green emission: crystal structure, photophysical interactions and DFT studies

Single crystal X-ray structurally characterised Fe3+ complex, [Fe(III)-TNESAL], derived from a multi-dentate tripodal imine (N,N',N'-tris-(2-aminoethyl)amine-tris-(3-ethoxysalicylideneimine, H(3)TNESAL) selectively recognizes Mg2+ through the generation of green fluorescence (lambda(em) = 488 nm) in HEPES buffered aqueous DMF (DMF/H2O, 3/1, v/v, 10 M HEPES buffer, and pH 8.1). The findings of the spectroscopic investigations suggest a metal ion displacement-based sensing mechanism in which Mg2+ relocates Fe3+ from the [Fe(III)-TNESAL] complex. The values for the detection limit and binding constant for Mg2+ are 7.66 x 10(-9) M and 1.56 x 10(5) M-1, respectively. The fluorescence lifetime of the [Mg(II)-TNESAL] complex is 4.99 ns. The TD-DFT studies endorse the experimental spectroscopic data.