Study of the electronic effect and quantitative spectra predictions of o-methoxyaniline-terminated monoazonaphthols: a combined experimental and DFT study

A combined experimental and density functional theory (DFT) study on the UV-Vis spectra of o-methoxyaniline-terminated mono azo dyes was conducted. By applying time-dependent-DFT calculations, details of excitation processes were determined and visualization by hole–electron analysis was undertaken. Fragment-divided analysis revealed the contributions of different parts of the structures for the UV-Vis spectra, that richer/poorer electron density on aromatic rings lead to greater/less maximum absorption wavelengths (λ(max)) and larger/smaller half peak width (W(1/2)). Combining theoretical prediction with experimental verification, we answered the question of how the electronegativities of substituents affected the electron densities and how it affected the spectra. In addition, a linear model connecting the λ(max) and W(1/2) to the chemical shifts obtained by NMR spectroscopy was constructed, which laid the foundation for construction of a spectral library.