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

Abstract

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, H₃TNESAL) selectively recognizes Mg²⁺ through the generation of green fluorescence (λ_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 × 10⁻⁹ M and 1.56 × 10⁵ 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.