Synthesis of Substituted N -Benzylidene- N' -(2,4 dinitrophenyl)hydrazine and their Acidochromic Behaviour

Substituted 2,4-dinitrophenylhydrazone Schiff bases were efficiently synthesized using microwave-induced organic reaction enhancement techniques. Different spectral techniques UV–Visible, Fourier transform infrared (FTIR), and 1HNMR) were used to analyze the prepared compounds (1a–1c). The hydrazone Schiff bases showed obvious acidochromic properties. The acidochromic behavior of substituted 2,4-dinitrophenylhydrazone Schiff bases were investigated by doping HCl in 3 different polar protic and aprotic solvent systems. The hyperchromic shift was observed in all three compounds in polar protic and aprotic solvent systems. In contrast to protic solvent, the hypsochromic shift was observed with an isosbestic point for all three compounds in polar aprotic solvent systems. These spectral changes can be attributed to successive protonation of the –C=N-chromophore. In order to probe this assumption, theoretical calculation was carried out using TD/DFT/ B3LYP/6-311+G(d,p) level of theory with different solvent system. For comparison the unprotonated and the protonated structure of UV–Vis spectra between computational and experimental findings were also performed. These results are in good agreement with the experimental data.