An Assessment of RASSCF and TDDFT Energies and Gradients on an Organic Donor–Acceptor Dye Assisted by Resonance Raman Spectroscopy

Abstract

The excitation energies and gradients in the ground and the first excited state of a novel donor-(π-bridge)-acceptor 4-methoxy-1,3-thiazole-based chromophore were investigated by means of MS-RASPT2/RASSCF and TDDFT in solution. Within both methods, the excitation energies strongly depend on the employed equilibrium structures, whose differences can be rationalized in terms of bond length alternation indexes. It is shown that functionals with an increased amount of exact exchange provide the best estimation of the ground and excited state properties. While B3LYP fails to predict the excitation energies due to its intrinsic problems in describing charge transfer (CT) states, the long-range corrected CAM-B3LYP and M06-2X functionals deliver good agreement with the experimental UV/vis absorption spectrum. The calculation of resonance Raman intensity patterns is used to discern which ground and excited state gradients are best. The results clearly evidence that both CAM-B3LYP and RASSCF excited state gradients and energies in combination with CAM-B3LYP ground state gradients are appropriate to describe the CT state of this push-pull chromophore.

Promising sensitizers for dye sensitized solar cells: A comparison of Ru(II) with other earth's scarce and abundant metal polypyridine complexes

“…The application of range-separated functionals, that is, CAM-B3LYP and ωB97XD, to transition metal complexes leads to a tremendous hypsochromic shift of all absorption features, while the relative error of local and MLCT states is preserved. [95][96][97] The calculated UV-Vis spectra showed a good agreement with the experiment and calculations performed by Pellegrin et al [15] for the anchors 1, 2, and 4 for the Ruthenium metal ion ( Figures S1 and S2). Recently, the ss-cLRPCM solvent model have been used by different researchers for TDDFT calculations that showed better results.…”

“…Our choice of functional and basis sets yields good agreement with experimental values with respect to λ(max) in the visible wavelength and the UV wavelength regime. The application of range‐separated functionals, that is, CAM‐B3LYP and ωB97XD, to transition metal complexes leads to a tremendous hypsochromic shift of all absorption features, while the relative error of local and MLCT states is preserved . The calculated UV‐Vis spectra showed a good agreement with the experiment and calculations performed by Pellegrin et al for the anchors 1, 2, and 4 for the Ruthenium metal ion (Figures S1 and S2).…”

TD-DFT benchmarks: A review

“…Recently, most CT investigations focussed on pinpointing an adequate hybrid (typically a RSH) . Nguyen and coworkers investigated 19 ES in donor‐acceptor complexes between TCE and aromatic compounds with a large panel of RSH and the cc‐pVDZ approach .…”

“…[253] Recently, most CT investigations focussed on pinpointing an adequate hybrid (typically a RSH). [136,140,114,182,184,197,201,239,[254][255][256][257][258] Nguyen and coworkers investigated 19 ES in donor-acceptor complexes between TCE and aromatic compounds with a large panel of RSH and the cc-pVDZ approach. [114] Besides demonstrating that basis set effects are small, the authors found that the two most effective methods were xB97X and LC-PBE that provided MAE below the 0.2 eV threshold, whereas all other RSH (CA-PBE, CA0-PBE, HSE, CAM-B3LYP, CA0-B3LYP, LC-xPBE, and xB97) gave significantly larger deviations.…”

Stacking Effects on Anthraquinone/DNA Charge-Transfer Electronically Excited States

“…For the QM calculation, the first 10 singlet excited states were computed at the TD-DFT level with the CAM-B3LYP [66] long-range corrected functional and Dunning's cc-pVTZ [67] basis set. The CAM-B3LYP functional was used since it has provided an excellent agreement with the experimental absorption spectra of many organic photosensitizers while providing a proper description of the charge-transfer states involved [68,69]. The characterization of the monomer, excimer, Frenkel exciton and charge-transfer states was performed by using the TheoDORE program suite [54,56].…”