| Abstract |
New arylhydrazones of beta-diketones, 5-chloro-3-(2-(1-ethoxy-1,3-dioxobutan-2-ylidene)hydrazinyl)-2-hydroxybe nzenesulfonic acid (1), 3-(2-(1-ethoxy-1,3-dioxobutan-2-ylidene)hydrazinyI)-2-hydroxy-5-nitroben zenesulfonic acid (2), and 3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene) hydrazinyI)-2-hydroxy-5-nitrobenzenesulfonic acid (3), have been synthesized and characterized by IR, H-1 and C-13 NMR spectroscopies and elemental analysis. 3 and known 5-(2-(4.4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-4-hydroxybenzene -1,3-disulfonic acid (4) exist in DMSO solution exclusively in the hydrazone form, while 1 and 2 exist in DMSO and H2O solutions as a mixture of enol-azo and hydrazone tautomeric forms, in ratios dependent on the solvent polarity and inductive effect of the substituents. DFT and TDDFT approaches were applied for simulations of experimental UV-VIS absorption spectra of the studied compounds, taking into account solvatochromic as well as tautomeric effect. The performed simulations have established a correlation of substantial experimental 120 nm red shift of the enol-azo form with respect to hydrazone with HOMO and LUMO orbitals delocalization. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved. |
