Tautomeric Study of Schiff Bases Derived from o‐Dihydroxybenzaldehyde by UV‐Vis, IR, ¹H NMR, ¹³C NMR Spectroscopy and Computational Modeling.

Abstract

Tautomeric equilibria at room temperature were studied for three aromatic imine polyol compounds, previously reported 2-((2-hydroxybenzylidene)amino)-2-(hydroxymethyl)propane-1,3diol 1 and two new compounds 2-(((1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)imino)methyl)benzene-1,4-diol 2 and 3-(((1,3-dihydroxy-2-(hydroxymethyl)propan-2 yl)imino) methyl)benzene-1,2-diol 3. The dynamic behavior of these equilibria is described by a combination of IR, UV-Vis and NMR spectroscopic measurements with DFT and TDDFT calculations in condensed phase. Among the different approaches, the combination of UV-Vis experimental spectra with the oscillator strengths values estimated from TDDFT calculations allowed for the assessment of the tautomeric populations in DMSO and methanol. These results were consistent with different functionals employed GGA, Hybrid and MetaGGA.

Novel Schiff Bases of C-Methylresorcinarene Derivatives

“…The band of conjugated imines appears at 375 nm, while the shoulder of The UV spectra of salRA and dmaeRA were studied the aprotic polar solvents DMF and acetonitrile, as well as in the protic solvent methanol (Figure 1c,d). The UV spectra of all Schiff base solutions show two absorption bands in the 300-500 nm range, which are related to π-π* transitions of the imine-and keto-tautomers [24,25]. For dmaeRA, the absorption band related to the transition of conjugated imine occurs at 330 nm.…”