Supramolecular Influence on Keto-Enol Tautomerism and Thermochromic Properties of o-Hydroxy Schiff Bases

• Main Authors: Marija Zbačnik, Branko Kaitner
• Format: Article
• Language: English
• Published: Croatian Chemical Society 2016-06-01
• Series: Croatica Chemica Acta
• Online Access: http://hrcak.srce.hr/file/235223

This work presents a study on thermo-optical properties of three Schiff bases (imines) in the solid state. The Schiff bases were obtained by means of mechanochemical synthesis using monosubstituted o-hydroxy aromatic aldehydes and monosubstituted aromatic amines. The keto-enol tautomerism and proton transfer via intramolecular O∙∙∙N hydrogen bond of the reported compounds was found to be influenced more by supramolecular interactions than by a temperature change. All products were characterised by powder X-ray diffraction (PXRD), FT-IR spectroscopy, thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Molecular and crystal structures of compounds <b>1</b>, <b>2</b> and <b>3</b> were determined by single crystal X-ray diffraction (SCXRD). The molecules of <b>1</b> appear to be present as the enol-imine, the molecules of <b>2</b> as the keto-amine tautomer and the molecules of <b>3</b> exhibit keto-enol tautomeric equilibrium in the solid state. An analysis of Cambridge structural database (CSD) data on similar imines has been used for structural comparison. <br><a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by/4.0/80x15.png" /></a> This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</a>.