UV-vis, IR and 1H NMR spectroscopic studies of some Schiff bases derivatives of 4-aminoantipyrine

Five Schiff bases derived from 4-aminoantipyrine and benzaldehyde derivatives (1) are prepared and their UV-vis, IR, H-1 NMR and fluorescence spectra are investigated and discussed. The electronic absorption spectra of the hydroxy 4-aminoantipyrine Schiff bases Ib and Ie as well as the fluorescence spectra of le are studied in the organic solvents of different polarity. The UV-vis absorption spectra of 4-aminoantipyrine Schiff bases Ib, Id and Ie are investigated in aqueous buffer solutions of varying pH and utilized for the determination of pK(a) and Delta G of the ionization process. The reactions of the hydroxy compounds Ib and Ie with Ni(II) and Cu(II) ions are also studied. The results of spectral studies are supported by some molecular orbital calculations using an atom superposition and electron delocalization molecular orbital theory for a compound Ib. (c) 2005 Elsevier B.V. All rights reserved.