Theoretical study of one- and two-photon absorption spectra of azoaromatic compounds

Abstract

Following the excited state relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy J. Chem. Phys. 135, 194307 (2011) Population inversion of molecular nitrogen in an Ar: N2 mixture by selective resonance-enhanced multiphoton ionization J. Appl. Phys. 110, 083112 (2011) Control of vibronic excitation using quantum-correlated photons J. Chem. Phys. 135, 164304 (2011) Resonant two-photon ionization spectroscopy of jet-cooled PdSi J. Chem. Phys. 135, 134308 (2011) Optical purification of a mixture of chiral forms by dimer formation J. Chem. Phys. 135, 124304 (2011) Additional information on J. Chem. Phys. In this study, the one-and two-photon absorption spectra of seven azoaromatic compounds ͑five pseudostilbenes-type and two aminoazobenzenes͒ were theoretically investigated using the density functional theory combined with the response functions formalism. The equilibrium molecular structure of each compound was obtained at three different levels of theory: Hartree-Fock, density functional theory ͑DFT͒, and Møller-Plesset 2. The effect of solvent on the equilibrium structure and the electronic transitions of the compounds were investigated using the polarizable continuum model. For the one-photon absorption, the allowed → ‫ء‬ transition energy showed to be dependent on the molecular structures and the effect of solvent, while the n → ‫ء‬ and → ‫ء‬ ͑n͒ transition energies exhibited only a slight dependence. An inversion between the bands corresponding to the → ‫ء‬ and n → ‫ء‬ states due to the effect of solvent was observed for the pseudostilbene-type compounds. To characterize the allowed two-photon absorption transitions for azoaromatic compounds, the response functions formalism combined with DFT using the hybrid B3LYP and PBE0 functionals and the long-range corrected CAM-B3LYP functional was employed. The theoretical results support the previous findings based on the three-state model. The model takes into account the ground and two electronic excited states and has already been used to describe and interpret the two-photon absorption spectrum of azoaromatic compounds. The highest energy two-photon allowed transition for the pseudostilbene-type compounds shows to be more effectively affected ͑ϳ20%͒ by the torsion of the molecular structure than the lowest allowed transition ͑ϳ10%͒. In order to elucidate the effect of the solvent on the two-photon absorption spectra, the lowest allowed two-photon transition ͑dipolar transition͒ for each compound was analyzed using a two-state approximation and the polarizable continuum model. The results obtained reveal that the effect of solvent increases drastically the two-photon cross-section of the dipolar transition of the pseudostilbene-type compounds. In general, the features of both one-and two-photon absorption spectra of the azoaromatic compounds are well reproduced by the theoretical calculations.

Two-photon brightness of azobenzene photoswitches designed for glutamate receptor optogenetics

“…S1). As in the parent compound Disperse Red 1, these data support assignment of n-π* and π-π* electronic transitions (37,38). We determined an extinction coefficient, e = 19,500 ± 500 M −1 cm −1 at 425 nm in DMSO.…”

“…These rules predict that the lowestenergy 1P-allowed π-π* transition should be strictly forbidden for 2P absorption (9). Molecular 2P absorption cross-sections (σ 2 ) in GoeppertMayer units ( (Table 1) are remarkably consistent with those of the parent compounds and related compounds from both classes of azobenzenes (36,38). Notably, the σ 2 of both MAGs are orders of magnitude larger than that of the most widely used caged neurotransmitter, MNI-glutamate (σ 2 Quantum Yield of MAG Photoisomerization.…”

“…Although the reduced symmetry of this photoswitch could relax the parity selection rules for π-π* transitions, our measurements are collectively more consistent with a highly blue-shifted n-π* band. The ordering of electronic states in pseudostilbenes is still debated (38), but electronic structure calculations on related molecules Disperse Red 1 and Disperse Orange 3 show significant population of an n-like HOMO-1 state (38). The character of these electronic transitions is significant for at least two reasons.…”

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

“…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.…”

“…[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. 31,33,39,42,43 When two lasers are used as the photon sources-as intended in e.g. 31,33,39,42,43 When two lasers are used as the photon sources-as intended in e.g.…”