Spectral-luminescent properties of pH-sensitive azo fluorophore in complexes with quaternary ammonium disinfectants

Abstract

Azo-based organic molecules offer broad-spectrum chemical and biological applications with excellent conjugated features. The present work reports the molecular chemical stability and relative polarity of potent azo compound, 2-amino-5-[(E)-(4-hydroxyphenyl)diazenyl]benzoic acid (AHABA), as well as its interaction mechanism with quaternary ammonium surfactants (Quats) at various pH conditions. The photoluminescent properties of yellow fluorophore, AHABA, in complexes with cetrimonium bromide (CTAB) and mecetronium bromide (EHDAB) were probed by quantifying its absorption and fluorescence emission spectra as a function of various concentrations of microheterogeneous assemblies. With the help of mathematical models, the stated interactions of combinational systems (AHABA–Quats) were quantified by estimating the partition coefficient (K x), the binding capacities (K b), Stern–Volmer quenching constant (K sv), and related free energies. The detailed investigation revealed that the binding and partition modes are spontaneous and the quenching mechanism is ascribed to the static quenching mode initiated by ground-state complex formation. Moreover, the results of molecular electrostatic potential (MEP) revealed that the hydrophilic character as well as the electrophilic attack on the subjected azo molecule increases as the pH of the medium increases. These findings extend the proficiency of subjected emitting fluorophore as a reporter for sensing electrostatic environment in lipidic membranes and related organized assemblies.