Stressing the differences in alizarin and purpurin dyes through UV-visible light absorption and 1 H-NMR spectroscopies

Abstract

Three anthraquinone-based chromophores (9,10-anthraquinone, alizarin, purpurin) are compared from the point of view of their experimental and computed NMR and UV-visible light absorption spectra. Using an hybrid (explicit/implicit) solvent model, each proton chemical shift can be reproduced with an error less than 7\%, even when such protons are engaged in inter-molecular hydrogen bonds with the solvent or when the analyzed sample contains a significant amount of impurities, for instance 9,10-anthraquinone in purpurin. All the steady-state UV-visible absorption spectra feature a significant vibrational progression in the first absorption band. The shape of the corresponding computed spectra, including vibronic couplings obtained with the Adiabatic Hessian approach and the Franck-Condon and Hertzberg-Teller approximation of the transition dipole, are in excellent agreement with the experimental one. The importance and the nature of the vibronic couplings are different for the three molecules, even if they only differ by the number of hydroxyl groups.

Rapid and complete prediction of Madder natural dyes’ color and properties through computational method

“…Tirri et al and Jacquemin et al have used DFT and TD-DFT to predict UV-Vis spectra attributes for a collection of chromophores including anthraquinones [5,[31][32][33][34][35][36][37][38]. The researchers tested various functional and basis sets, concluding that B3LYP and PBE0 are well-suited for predicting the electronic properties of the anthraquinone family, with an error less than 0.2 eV [22,39,[39][40][41]. The existence of different tautomer were also studied by J.…”

“…The existence of different tautomer were also studied by J. [22,[42][43][44]. The literature about the studies of dyes and UV-Vis spectra are abundant but most of the studies don't focus explicitly on the influence of the choice of solvation model which is important to accurately simulate the real phenomena.…”