The Role of Molecular Conformation and Polarizable Embedding for One- and Two-Photon Absorption of Disperse Orange 3 in Solution

Abstract

Solvent effects on the one- and two-photon absorption (1PA and 2PA) of disperse orange 3 (DO3) in dimethyl sulfoxide (DMSO) are studied using a discrete polarizable embedding (PE) response theory. The scheme comprises a quantum region containing the chromophore and an atomically granulated classical region for the solvent accounting for full interactions within and between the two regions. Either classical molecular dynamics (MD) or hybrid Car-Parrinello (CP) quantum/classical (QM/MM) molecular dynamics simulations are employed to describe the solvation of DO3 in DMSO, allowing for an analysis of the effect of the intermolecular short-range repulsion, long-range attraction, and electrostatic interactions on the conformational changes of the chromophore and also the effect of the solute-solvent polarization. PE linear response calculations are performed to verify the character, solvatochromic shift, and overlap of the two lowest energy transitions responsible for the linear absorption spectrum of DO3 in DMSO in the visible spectral region. Results of the PE linear and quadratic response calculations, performed using uncorrelated solute-solvent configurations sampled from either the classical or hybrid CP QM/MM MD simulations, are used to estimate the width of the line shape function of the two electronic lowest energy excited states, which allow a prediction of the 2PA cross-sections without the use of empirical parameters. Appropriate exchange-correlation functionals have been employed in order to describe the charge-transfer process following the electronic transitions of the chromophore in solution.

Simulating One-Photon Absorption and Resonance Raman Scattering Spectra Using Analytical Excited State Energy Gradients within Time-Dependent Density Functional Theory

“…Such effects, including both explicit and bulk interactions, which have been included in several previous studies of absorption and emission processes, have been demonstrated to be important. 46,49,101,102 The RRS spectrum (Figure 4b) shows good agreement with the experimental spectrum. The four most prominent features (528, 990, 1398, and 1505 cm −1 ) are vibronically coupled to the electronic transition, and this is captured in the simulation.…”

“…While the simulations presented here neglect environmental effects, such as implicit or explicit solvation, this only has a small effect on the results presented in this section. It should be stressed that in situations where simulated results are compared with experiments measured in polar solvents or where environmental interactions are important, solvation effects generally must be included for accurate results 46,101,102. …”

Benchmarking two-photon absorption cross sections: performance of CC2 and CAM-B3LYP

“…30,32,36,39 What is usually done, however, is choosing a single empirical parameter for G, often chosen to be 0.1 eV, 13,14,18,21,22,28,29,37,38 but also other broadening factors have been used, usually taken from the broadening of a specific peak in an experimental spectrum. 30,32,36,39 What is usually done, however, is choosing a single empirical parameter for G, often chosen to be 0.1 eV, 13,14,18,21,22,28,29,37,38 but also other broadening factors have been used, usually taken from the broadening of a specific peak in an experimental spectrum.…”

“…19,21 This corresponds to an experimental setup with two laser sources (a so-called doublebeam experiment 41 ), thus in principle allowing for two photons with different energies. [30][31][32][33]39,42,43 In fact, the photon dissipation rate is in this case twice the calculated twophoton absorption rate because two photons together excite the molecule. [30][31][32][33]39,42,43 In fact, the photon dissipation rate is in this case twice the calculated twophoton absorption rate because two photons together excite the molecule.…”

“…The use of eqn (14) instead of eqn (3) leads to hd TPA i-which depends on terms of S times % S-lower by a factor of 4. 30,32,34 This is the strategy implemented in e.g. 30,32,34 This is the strategy implemented in e.g.…”