Kinetics of the dark cis–trans isomerization of azobenzene and azo pyridine derivatives in ethanol and chloroform solutions
Jolanta Konieczkowska, Anna Wasiak, Anna Sobolewska, Stanisław Bartkiewicz, J.G. Małecki, Ewa Schab‐Balcerzak
Abstract
The paper presents a series of azobenzene and azo pyridine compounds containing hydroxyl or 6-hydroxyhexyloxyl substituents. The nitrogen atom is located at the ortho-, meta- or para-position in the structure of azo pyridine derivatives. The impact of the structural features of azo chromophores on their thermal (DSC, TGA) and optical (UV–Vis) properties was investigated. The dark cis–trans isomerization kinetics was studied in ethanol and chloroform at 298 K. The formation of noncovalent hydrogen bonds between azo molecules and/or chromophore-solvent was monitored using the 1H NMR spectroscopy and estimated by density functional theory (DFT) calculations. Based on experimental and computational studies we proposed the mechanism of the dark cis–trans isomerization for hydroxy-substituted azo compounds.