Pyrimidine-based azo dyes: Synthesis, photophysical investigations, solvatochromism explorations and anti-bacterial activity

Abstract

Azo dyes are widely recognized for their diverse applications, including colorants, sensors, and imaging agents. The unique molecular structure of pyrimidine-based azo dyes offers intriguing possibilities for tuning their optical properties through strategic modifications. The synthesis of a series of pyrimidine-based azo dyes was carried out using well-established methods, and the chemical structures were confirmed by various spectroscopic techniques. To the best of our knowledge, for the first time such type of electron-rich azo dyes with a pyrimidine-based framework were probed for their solvatochromism and fluorescent behaviors. Subsequently, their photophysical properties were investigated using UV–visible absorption and fluorescence spectroscopy. The solvatochromic effect revealed significant changes in the dyes' absorption and emission wavelengths, providing valuable information about their polarity-dependent behavior. To establish correlations between molecular structure and optical properties, a thorough analysis of the obtained data was conducted. Their emission characteristics were also analyzed to assess their suitability as fluorescent probes. Azo dyes (7-12) demonstrate a remarkable ability to efficiently convert absorbed energy into emitted light, as indicated by their high quantum yield values. Biological investigations have demonstrated significant efficacy against a wide range of bacterial strains, with their performance comparable to that of commercially available antibiotics such as Cefixime. Structure-activity & -property relationships were delineated, highlighting the impact of specific molecular modifications on the biological and photophysical behaviors of the reported dyes.