A set of azo dyes were prepared by diazotization of a series of electronically different substituted anilines and subsequent azo coupling of these diazonium salts with ethyl 4,5-dihydro-5-oxo-2-aryl(1H)pyrrole-3-carboxylate as a the coupling component. All of the dyes were confirmed as keto-hydrazone tautomers and were found as a mixtures of E- and Z- isomers with respect to the exocyclic C=N bond by 1H NMR spectroscopy. The absorption spectra are all similar irrespective of substituent and solvent. By comparison the fluorescence is strongly dependent on the electronic character of the substituents. All compounds fluoresce in a low temperature solvent glass and in the solid state except the ortho hydroxyl and ortho nitro derivatives and only the 4-cyanophenyl and 4-nitrophenyl derivatives show fluorescence in solution at room temperature. The spectroscopic behavior is explained in terms of competition between E/Z isomerisation and fluorescence after excitation.
In the second part of this work short series of cobalt and chromium complex dyes based on pyrrolinone ring was prepared; the synthesis of these compounds was based on using pure hydrazone dyes as starting ligand. Multinuclear magnetic resonance spectroscopy (NMR) technique was very useful for proving the structure of prepared compounds. In contrast to the starting compounds existing ligands completely in hydrazone form, cobalt (III) complexes exist in (E)-azo configuration and cobalt atom is six-coordinated being bound to oxygens, which originate in hydroxyl and CONH groups and nitrogens from substituted anilines as starting material from two ligands. Spectral properties of these compounds were studied as well as photochemical isomerisation using absorption spectra.
