The prototropic tautomerism and substituent effect through strong electron-withdrawing group in (E)-5-(diethylamino)-2-[(3-nitrophenylimino)methyl]phenol

• Prototropic tautomerism is experimentally and theoretically investigated.
• The effect of substituent is emphasized on proton transfer process.
• The supramolecular structure of title compound is investigated.

The prototropic tautomerism in o-Hydroxy Schiff bases results in two forms called phenol-imine and keto-amine. The preference of a particular form by the compound changes in the solid and solvent media. The choice can also be regulated by a substituent with a different electron-donating or withdrawing group. In the present study, the above-mentioned factors are considered in the investigation of (E)-5-(diethylamino)-2-[(3-nitrophenylimino)methyl]phenol compound (an o-Hydroxy Schiff basis) by experimental (XRD, FT-IR and UV–vis) and computational (DFT and TD-DFT) methods. The results show that the title compound adopts only phenol-imine form in the solid and solvent media. This was attributed to the substituent effect through strong electron-withdrawing nitro group.

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