Spectral and structural characterization of 2-(fluorophenylamino)- and 2-(nitrophenylamino)-1,4-naphthoquinone derivatives

• Novel 2-(nitrophenylamino)-1,4-naphthoquinones derivatives were synthesized and characterized.
• Solvent impact on absorbance and emission napthoquinone derivatives is assessed.
• The charge transfer transition is most sensitive to solvent and substituents.
• Quantum calculations confirm the spectral assignments and substituent effects.

Naphthoquinone amino derivatives exhibit interesting physicochemical properties and are of interest for potential medicinal purposes. The preparation of novel 2-(nitrophenylamino)-1,4-naphthoquinones derivatives was achieved by reaction of nitroanilines with 1,4-naphthoquinone with a catalytic amount of FeCl3 or by direct nitration of 2-(phenylamino)-1,4-naphthoquinone (PAN). Structural and photophysical properties of a series of NO2PANs and FPANs derivatives are examined using computational and spectroscopic methods. Absorbance and emission spectra are measured in a range of solvent environments to examine the impact of solvent–solute interactions. Additionally quantum calculations are used to evaluate the electronic nature of the spectral transitions and compare structures of the different PAN derivatives. The lowest energy electronic transitions have charge transfer character, and show the most sensitivity to solvent and substituents. Higher energy π–π* transitions are relatively insensitive to both factors. Computational predictions are in good agreement with the experimental spectra, and provide molecular-level insight variations amongst the different aniline-substituents.

A series of novel 2-(nitrophenylamino)-1,4-naphthoquinones derivatives was synthesized, and their photophysical properties examined using computational and spectroscopic methods.Figure optionsDownload as PowerPoint slide