Synthesis and crystal structures of a series of Schiff bases: a photo-, solvato- and acidochromic compound

Abstract

Seven Schiff base derivatives of 4-dimethylamino-trans-cinnamaldehyde were synthesized in good yield. The structures of all new derivatives were established by IR, ¹H, ¹³C NMR and HRMS experiments and three of them were corroborated by X-ray diffraction studies. Analysis of the supramolecular structures evidenced the presence of strong intermolecular hydrogen bonds (O–H⋯N) which promote the formation of molecular chains. The linear properties of this series of chromophores were investigated by UV-Vis and fluorescence spectroscopy in solution and in the solid state. The results revealed interesting photochromic properties for compound 2a promoted by a hydrogen bonding interaction in the solid state, which was established by absorption and emission spectra. Further evidence of the specific interactions that take place in compound 2a was obtained by studying the solvent effects observing a solvato- and acidochromic behavior.