pH-sensitive 4,(4-Nitrophenoxy)benzeneamine) derived azo dye: X-ray crystallographic, DFT and electrochemical studies

A novel nitro terminated azo dye, (E)-3-((4-(4-nitrophenoxy)phenyl)diazenyl)-[1,1′-biphenyl]-4-ol (1), was produced by coupling biphenyl-4-ol with 4,(4-Nitrophenoxy)benzeneamine) and was characterized by various spectroscopic and XRD technique. The chemical structure of the compound (1) has a nitro terminal as an electron-withdrawing moiety (A), a biphenyl ring of coupling part as a proton-donating unit (D), and both groups are linked by an azo group connector. The stimulating pH-controlled absorption behavior of chemosensor was investigated using UV/VIS spectroscopic technique. It was observed that synthesized dye (1) has high sensitivity in pH range from 7.9 to 10.46 and could be applied as a selective ‘naked-eye’ colorimetric sensor for H+ ion concentration, as it exhibited a very strong hyperchromic shift in the absorption band from 399 nm to 521 nm with a significant color change from yellow to red. The sensitivity of chemosensor was observed to be fully reversible and rapid which enhance its chances of practical implicitly. Further, DFT simulations were performed using ADF-Modeling suite 2019, to get an idea of relevance with experiments. Additionally, redox behavior of the (1) dye was also investigated by employing cyclic voltammetry using 0.1M TBAP as supporting electrolyte. Cis–Trans conformational changes were analyzed to investigate the photoisomerization ability of the synthesized dye. •Nitro terminated azo dye was synthesized by classical diazotization-coupling strategy.•Spectral studies revealed the compound to be pH sensitive in the range 7.9–10.46•Computed DFT simulation showed good relevance with UV spectra.•Redox activity was shown by Voltammetry.