Assessing the Performance of DFT Functionals for Excited-State Properties of Pyridine-Thiophene Oligomers

Abstract

In this article, we have examined the accuracy of various density functional theory (DFT) functionals to reproduce the absorption and CD spectra of pyridine-thiophene oligomers. The performance of different levels of approximations in DFT functionals is discussed with reference to the ADC(2) results. Starting from a linear system, like monomer, calculations are carried out at ADC(2) and DFT levels till a helical system, like pentamer, is formed. For vertical excitation energies, results obtained with functionals, like CAM-B3LYP, ωB97XD, and M06-2X, are closer to the ADC(2) results. However, analysis of excited-state properties shows that the state ordering patterns or results regarding natural transition orbitals from these DFT functionals sometimes differ from the ADC(2) results. Global hybrid functionals like B3LYP and PBE0 produce excitation energies which are far away from the ADC(2) benchmark results. Similarly, pure functionals and their long-range corrected versions produce either redshifted or blueshifted energies. For the CD spectra, the above three mentioned functionals, CAM-B3LYP, ωB97XD, and M06-2X, again produce spectra closer to the benchmark spectra.

Absolute configuration of a [1]rotaxane determined from vibrational and electronic circular dichroism spectra

“…The simulated ECD bands for ( S , R mp )‐ 1 show great agreement at the B3LYP/6‐31G* level, a level of theory that has been shown to have large errors for charge‐transfer interactions in the calculation of Rydberg states 38–40 . To test the validity of our results at the B3LYP/6‐31G* level, we carried out additional single‐point TD‐DFT calculations on the lowest energy structures of ( S , R mp )‐ and ( S , S mp )‐ 1 at the CAM‐B3LYP/6‐31G* level using the previously calculated B3LY/6‐31G* optimized geometries.…”

Photochemical Synthesis and Electrochemical and Photophysical Properties of 2,7-Diarylbenzo[1,2-d:4,3-d′]bis(thiazoles)

“…To determine the lowest-energy conformers of the studied benzobisthiazoles, a systematic conformational analysis has been conducted using the M06-2X hybrid functional (see Computational Details). This functional demonstrates an excellent performance to describe excited state geometries and electronic properties of organic compounds and, in particular, thiophene-based oligomers. , It is widely accepted that 2,2′-bithiophene compounds prefer anti conformation, , thus the key issue is the preferential orientation of the central core and the nearest thiophene ring. Computations revealed that for 9c and 8c molecules, the anti–anti (AA) conformer is the most stable one.…”

“…This functional demonstrates an excellent performance to describe excited state geometries and electronic properties of organic compounds and, in particular, thiophene-based oligomers. 49,50 It is widely accepted that 2,2′-bithiophene compounds prefer anti conformation, 51,52 thus the key issue is the preferential orientation of the central core and the nearest thiophene ring.…”

Effects of Heterocyclic Ring Fusion and Chain Elongation on Chiroptical Properties of Polyaza[9]helicene: A Computational Study

“…It is well-known that the linear-response TD-DFT method using standard DFT functionals has inherent deficiencies, e.g., to describe closely located excited states, , states comprising of multiple excitations, ,− charge-transfer excited states, − and extended π-conjugated systems. In these scenarios, range-separated functionals such as CAM-B3LYP and ωB97XD have been shown to work better. ,− In our case, to verify the applicability of DFT functionals, vertical excitation calculations were also carried out at the second-order algebraic diagrammatic construction schemes for the polarization propagator ADC(2) , level using the same basis set. Resolution-of-the-identity (RI) approximation was used in the ADC(2) calculations.…”