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Keywords:

  • azobenzene;
  • absorption spectra;
  • TD-DFT;
  • PCM;
  • tautomers;
  • isomers

Abstract

Using time-dependent density functional theory and the polarizable continuum model, we have simulated the absorption spectra of an extended series of azobenzene dyes. First, we have determined a theoretical level optimal for this important class of dyes, and it turned out that a C-PCM-CAM-B3LYP/6-311+G(d,p)//C-PCM-B3LYP/6-311G(d,p) approach represents an effective compromise between chemical accuracy and computational cost. In a second stage, we have compared the theoretical and experimental transition energies for 46 n [RIGHTWARDS ARROW] π and 141 π [RIGHTWARDS ARROW] π excitations. For the full set, that spans over a 302–565 nm domain, we obtained a mean absolute deviation of 13 nm (0.10 eV) and a linear correlation coefficient of 0.95, illustrating the accuracy of our approach, though some significant outliers pertained. In a last step, the impact of several modifications, that is, trans/cis isomerization, variation of the acidity of the medium and azo/hydrazo tautomerism have been modeled with two functionals. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010