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Keywords:

  • QM/MM method;
  • solvent effects;
  • dipole moments;
  • benzotriazole

Abstract

Sequential Monte Carlo and quantum mechanical calculations of the electronic polarization of the ground and first vertical excited states of 1H-benzotriazole in water are made. Using statistically uncorrelated configurations and CASSCF ab initio calculations the increase in the ground and excited state dipole moments of 1H-benzotriazole from gas phase to aqueous environment are obtained as 2.89 ± 0.10 and 2.75 ± 0.11 D, leading to total moments of 6.89 ± 0.10 and 6.40 ± 0.11 D, respectively. Structures are sampled using the statistical correlation interval obtained from the autocorrelation function of the energy and statistical convergence of the calculated dipole moments is shown. These water-polarized dipole moments of 1H-benzotriazole are used to obtain the solvatochromic shift of the first absorption transition. The resulting theoretical blue shift of 570 cm−1 for the strong and characteristic π [RIGHTWARDS ARROW] π* transition is in good agreement with the inferred experimental value of ∼700 cm−1. The use of the gas-phase values of the dipole moments are useful for the qualitative understanding of the shift but the polarization of the solvent is required to achieve quantitative agreement. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003