Controlled shift in the tautomeric equilibrium of 4-((phenylimino)methyl)naphthalen-1-ol

• Published in: Journal of molecular structure Vol. 1036; pp. 267 - 273
• Main Authors: Deneva, V., Manolova, Y., Lubenov, L., Kuteva, V., Kamounah, F.S., Nikolova, R., Shivachev, B., Antonov, L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 27-03-2013
• Subjects: absorption; acetonitrile; Alkali and alkaline earth metal salts; Molecular spectroscopy; nuclear magnetic resonance spectroscopy; Schiff bases; Tautomerism; X-ray crystallography; X-ray diffraction; X-ray crystallography; Schiff bases; Molecular spectroscopy; Tautomerism; Alkali and alkaline earth metal salts
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2012.11.055

► 4-((Phenylimino)methyl)-2-(piperidin-1-ylmethyl)naphthalen-1-ol was studied. ► The controlled shift of the tautomeric equilibrium through structural modifications was achieved. ► The inclusion of the piperidine ring leads to shift of the equilibrium to the enol tautomer. ► Upon protonation the equilibrium shifts to the keto tautomer in a controlled and reversible manner. ► The salt addition leads to shift in the tautomeric equilibrium, independly on the kind of salt used.
4-((Phenylimino)methyl)naphthalen-1-ol and 4-((phenylimino)methyl)-2-(piperidin-1-ylmethyl)naphthalen-1-ol have been synthesized and their tautomeric properties were investigated using molecular spectroscopy (UV–Vis absorption/emission and NMR), X-ray crystallographic analysis and quantum-chemical calculations. The results show that with the implementation of a flexible piperidine ring a controlled shift in the tautomeric equilibrium will be achieved upon protonation/deprotonation in acetonitrile. The addition of a metal salt also shifts the tautomeric equilibrium, but at very high concentrations, which is caused not by a complex formation, but a special effect of the salt addition.