2020 Volume 36 Issue 6 Pages 659-666
Two novel malonyl-based chemosensors, N,N′-bis(ethyl-4′-benzoate)-1,3-propanediamide (1) and N,N′-bis(ethyl-3′-benzoate)-1,3-propanediamide (2), have been synthesized and screened towards various biologically important metal ions such as Na+, Mg2+, K+, Ca2+, Al3+, Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Cd2+, Hg2+, Ti3+, and Pb2+. The emission spectral studies of both 1 and 2 displayed 84 – 91% turn-off emission responses selectively with Fe3+ ion in aqueous buffer (MeCN/H2O, 1:4, v/v, pH = 7.4) solution. Chemosensors 1 and 2 exhibited remarkable sensing ability towards Fe3+ ion over other metal ions with limit of detection (LOD) of 4.28 and 4.33 μM, respectively. The binding stoichiometry of 1 and 2 with Fe3+ ion was studied by Benesi–Hildebrand fitting, Stern–Volmer plot and Job’s plots, revealing that both chemosensors (1 – 2) bind with Fe3+ metal ion in 1:1 stoichiometric ratio with the apparent association constant (Ka) 8.90 × 103 and 11.16 × 103 M−1, respectively. Furthermore, the interactions of chemosensors (1 – 2) with metal ion were also investigated by using density functional theory (DFT) at B3LYP hybrid functional using 6-31G and LanL2DZ basis sets.