Synthesis, Spectral Studies and Application of Schiff-Base Derived Ligand For Sensing of Hydrogen Carbonate Anion

The Schiff-base ligands, owning good donor properties, are very important in coordination chemistry [1]. Azo-benzenes are used in the chemical industry as dyes and pigments, drugs, food additives, liquid crystals, photochemical molecular switches, and nonlinear optics [2]. In this study, at first, the synthesis and characterization of Schiff- Base ligand (L1), containing N = N and C = N dye units with OH and NH groups, from the condensation reaction 2-amino-3-methylpyridine has been reported with salicylic aldehyde derivatives.Then, the sensor behavior of the (L1) ligand against the HCO3− anion was investigated by the UV-Vis (Fig.1), 1H—NMR techniques. The (L1) ligand exhibited significant color and spectral variations with respect to the HCO3− anion in DMF / H2O solution (95: 5) (Fig.2). A significant change in the color of the DMF / H2O solution of the other anions, such as: F −, Cl −, Br −, HSO4 −, N3 −, NO2 −, H2PO4−, SCN−, ClO4−and NO3− was not observed.The nature of the interaction of (L1) receptor with hydrogen Carbonate anion was confirmed through hydrogen bonding. By using the changes in the absorption spectrum, the stability constant (Ka) and the stoichiometric ratio of the host-guest complexes were determined with the Bensi-Hildebrand diagram and the Jobs plot curve method, respectively.