Dual Canal Schiff Base Chemosensor of N,N'-Bis(4-Isopropylbenzylidene)-2,3-Diaminopyridene (BIPBDAP) and its...

The metal ion sensing behaviour of the receptor N,N'-Bis(4-Isopropylbenzylidene)-2,3-Diaminopyridine (BIPBDAP) was studied by UV-Vis and fluorescence spectroscopic methods. The receptor BIPBDAP was found to detect selectively Fe(III) and Al(III) ions over other metal ions such as Na(I), Mg(II), Ca(II), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Sr(II), Cd(II), Ba(II), Hg(II), and Pb(II). The stoichiometry of the complex formed between the receptor and the metal ion is 2:1 and can be authenticated by the Job's Plot method. The association constants of Al(III) and Fe(III) ions with the receptor were evaluated using the Benesi-Hildebrand plot and its equation, as 1.23 × 10⁵M^- 1 and 1.08 × 10⁴M^- 1, respectively. The detection limits of the receptor with Al(III) and Fe(III) ions were found to be 8.285 × 10^- 7 M and 3.737 × 10^- 7 M, respectively. The structure of the Schiff base was optimised by using DFT. The DFT method is used to determine the Mulliken charges, HOMO, LUMO, molecular electrostatic potential and contour diagram. DFT calculations were performed using the GAUSSIAN09 program package using B3LYP level with 6-31G(d, p) as the basis set. The intermolecular charge transfer processes can be explained by Mulliken charge population analysis. The softness and reactivity of BIPBDAP are confirmed by the smallest HOMO-LUMO energy gap. Electron delocalisation is substantiated by MEP, ESP and total density maps.