Theoretical computation of Betain B30 solvatochromism using a Polarizable Continuum Model

• The absorption spectrum of Betain B30 in fifty-four organic solvents was simulated.
• The huge solvatochromic effect of this compound was demonstrated.
• A theoretical correlation between the intrinsic molar transition energy and the dielectric constant of a solvent was obtained.
• This correlation was found to be in good agreement with the experiments.

We report in this paper the computation of optical properties of a solvatochromic probe using Time-Dependent Density Functional Theory methodology. Our protocol includes the use of an implicit solvent model to take into account the surrounding effects on the physical behavior of the considered molecules. Because this compound presents a long-range net charge separation in the ground state, preliminary benchmark calculations involving meta-GGA, hybrid, range-separated and dispersion-corrected functionals were used to determine electronic structures and to evaluate the vertical transition energies. Since the molecular target exhibits a very large negative solvatochromism, its absorption range among fifty-four organic solvents was screened. Topological considerations based on natural transition orbitals concerning the involved excited states are also presented. Thenceforward the value of the Dimroth–Reichardt index, a macroscopic empirical quantity related to the light absorption of this compound was predicted. Finally, the dipole moment variation during the electronic transitions was characterized, explaining the noteworthy solvatochromism of these molecules.

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