Computing the inhomogeneous broadening of electronic transitions in solution: a first-principle quantum mechanical approach

Abstract

Starting from Marcus's relationship connecting the inhomogeneous broadening with the solvent reorganization energy and exploiting recent state-specific developments in PCM/TD-DFT calculations, we propose a procedure to estimate the polar broadening of optical transitions. When applied to two representative molecular probes, coumarin C153 and 4-aminophthalimide, in different solvents, our approach provides for the polar broadening values fully consistent with the experimental ones. Thanks to these achievements, for the first time fully ab initio vibrationally resolved absorption spectra in solution are computed, obtaining spectra for coumarin C153 in remarkable agreement with experiments.

Benchmarking TD-DFT against Vibrationally Resolved Absorption Spectra at Room Temperature: 7-Aminocoumarins as Test Cases

“…The employment of larger HWHM in polar solvents with respect to apolar ones is justified by Marcus's relationship that connects the inhomogeneous broadening with the solvent reorganization energy, which is bigger for polar solvents. 75,76 The stick spectra are similar to those computed in methylcyclohexane, but they are spread over a larger spectral interval, and new combined transitions appear. In fact, the peaks of the C307 molecule associated with the simultaneous excitation of modes 20−16, 75−16, and 75−20 found, respectively, at 707, 2029, and 2141 cm −1 from the 0−0 transitions show stronger intensities, and this is also the case for the peak at 3463 cm −1 from the 0−0 transition associated with the double excitation of mode 75. In the case of C460, the change in solvent polarity leads to more intense peaks for the transitions associated with the single excitation of mode 79, to the simultaneous excitation of modes 79−23 (2244 cm −1 ), and to the double excitation of mode 79 (3451 cm −1 ).…”

Excitation Dynamics in Hetero‐bichromophoric Calixarene Systems

“…The values obtained with the former method would critically depend on the linewidth attached to the vibronic bands. Obtaining an on-phenomenological estimation of such broadening is stillachallenging task, [63,64] especially in systemsa sc omplex as those investigated. Therefore, we preferred to rely on experimental data (Table 6) Some preliminary considerations are necessary before discussingt he results.…”

A State-Specific PCM–DFT method to include dynamic solvent effects in the calculation of ionization energies: Application to DNA bases

“…We report a suitably modified version of StateSpecific PCM-DFT (SS-PCM/DFT), which, in his time dependent (TD) version, has already provided very accurate estimates of dynamical solvent effect on absorption and emission spectra of several molecular systems in solution [10][11][12][13], and has been implemented in commercially available packages. The SS-PCM-DFT method is particularly appropriate because it allows calculation of both the ground and the excited states of the cation at the same quantum level.…”