Clean and Efficient Green Protocol of <i>N</i>,<i>N</i>′-Bis(2-(arylazo)-2-(aroyl)vinyl)ethane-1,2-diamines in Aqueous Medium without Catalyst: Synthesis and Photophysical Characterization

An interesting platform for the construction of novel <i>N</i>,<i>N</i>'-bis(2-(arylazo)-2-(aroyl)vinyl)ethane-1,2-diamines is reported in this work. These bis-arylazo compounds were assembled based on the reaction of ethylenediamine with various 2-arylhydrazono-3-oxopropanals in aqueous conditions under both conventional stirring and microwave conditions at ambient temperature. The factors affecting the optimization conditions were intensively practiced. The structures of the new products were established from their spectroscopic analyses and X-ray single crystals. The photophysical behavior of the bis-arylazo derivatives was examined. The UV-vis spectra showed maximum absorption band in the range of 348-383 nm with molar extinction coefficients ranging from 0.89 × 10⁴ to 4.02 × 10⁴ M^-1 cm^-1. The highest molar absorptivity coefficient (∼45 × 10³ M^-1 cm^-1) was observed in CHCl₃ solvent. The fluorescence properties showed that some compounds were interesting fluorophore materials with high Stokes shifts. The photoluminescence study of some compounds was promising, with maximal emission peaks ranging between 417-436 nm.