Computing UV–vis spectra of 1-bromo-1-propene: a comparison of model core potential and all-electron basis sets

Vacuum ultraviolet (VUV) spectroscopy can be used to identify different isomers in complicated mixtures of many molecules. In this work, calculated VUV spectra are compared with spectra of experimental mixtures to benchmark appropriate computational methods. Because the benchmark molecule, 1-bromo-1-propene, contains a heavy atom, both all-electron and model core potential basis sets were investigated. Time-dependent density functional theory (TD-DFT) can accurately compute electronic excited states at low-energy excitations and was cross-checked at higher energies against results from the symmetry adapted cluster–configuration interaction (SAC–CI) method. TD-DFT was determined to be satisfactory at low energies; however, excitation energies can deviate by 0.5 eV at high energies. TD-DFT with both all-electron and model core potential basis sets produced satisfactory excitation energies for the lower excited states. This method is also satisfactory at predicting spectra produced experimentally, including a mixture of isomers (cis- and trans-1-bromo-1-propene), with the exception of underestimating oscillator strength.

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ABSORPTION OF SOME SMALL SILVER CLUSTERS: DFT AND CASPT2 CALCULATIONS

Vietnam Journal of Science and Technology ◽

10.15625/2525-2518/55/6a/12367 ◽

2018 ◽

Vol 55 (6A) ◽

pp. 72

Author(s):

Ngo Tuan Cuong

Keyword(s):

Absorption Spectra ◽

Density Functional ◽

Noble Gas ◽

Silver Cluster ◽

Dft Method ◽

Basis Sets ◽

Silver Clusters ◽

Excitation Energies ◽

Complete Active Space ◽

Td Dft

Two quantum chemical methods which are the time-dependent density functional theory (TD-DFT) and the complete active space CASPT2/CASSCF have been used in modeling absorption spectra of silver clusters Agn (n = 2, 3, 4, 6, 8). There is an overall good agreement between TD-DFT and CASPT2 results for transition energies. The absorption spectra of the Agn clusters examined can reasonably be simulated using the excitation energies obtained by either TD-DFT or CASPT2 method. The main result emerged from this calculation is that the TD-DFT method is suitable for treatment of excited states of Ag clusters. The choice of specific functionals and basis sets to be used in some cases induces important effects on the calculated spectra. It is also noteworthy to mention that for some clusters, the neutral Ag6 for instance, the effect of noble gas environment is significant, while for some others such as the neutral Ag8, it is not. Therefore, carrying out TD-DFT calculations to reproduce and to assign a given structure to an experimental absorption spectrum of a silver cluster, it is not only to select suitable functionals but also to take enough effects of environments into account.

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A Theoretical Study on Photosensitizers of Solar-Energy Cell: Transition Metal Carboxyphthalocyanine Complexes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.415-417.1287 ◽

2011 ◽

Vol 415-417 ◽

pp. 1287-1290

Author(s):

Li Chun Xuan ◽

Yuan Ru Guo ◽

Qing Jiang Pan

Keyword(s):

Transition Metal ◽

Density Functional ◽

Red Light ◽

Dye Sensitized Solar Cells ◽

Basis Sets ◽

Excitation Energies ◽

Light Region ◽

Td Dft ◽

Zinc Cadmium ◽

Sensitized Solar Cells

Transition metal phthalocyanine complexes have been applied in the dye-sensitized solar cells (DSSCs), owing to their high absorbance coefficient in red-light region, good thermodynamic stability and facile synthesis. Structures of carboxyphthalocyanine complexes containing zinc, cadmium and mercury were optimized using the B3LYP functional. The M-N distances (M = Zn, Cd and Hg) were calculated to be 2.03, 2.12 and 2.16 Å, respectively. On the basis of these geometries, the electronic spectra in ethanol were predicted at the time-dependent density functional theory (TD-DFT) level. It was shown that the variation of Zn→Cd→Hg changes the transition nature of lower-energy absorption, but slightly affects the excitation energies. In addition, the effects of basis sets (Lan2DZ and SDD), solvent-effect models (PCM and CPCM) and solvents (ethanol and methanol) on absorption spectra were discussed in detail.

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Excited States Computation of Models of Phenylalanine Protein Chains: TD-DFT and Composite CC2/TD-DFT Protocols

International Journal of Molecular Sciences ◽

10.3390/ijms23020621 ◽

2022 ◽

Vol 23 (2) ◽

pp. 621

Author(s):

Marine Lebel ◽

Thibaut Very ◽

Eric Gloaguen ◽

Benjamin Tardivel ◽

Michel Mons ◽

...

Keyword(s):

Excited States ◽

Potential Energy Surfaces ◽

Density Functional ◽

Vibrational Energy ◽

Zero Point ◽

Quantitative Agreement ◽

Geometrical Parameters ◽

Excitation Energies ◽

Dft Methods ◽

Td Dft

The present benchmark calculations testify to the validity of time-dependent density functional theory (TD-DFT) when exploring the low-lying excited states potential energy surfaces of models of phenylalanine protein chains. Among three functionals suitable for systems exhibiting charge-transfer excited states, LC-ωPBE, CAM-B3LYP, and ωB97X-D, which were tested on a reference peptide system, we selected the ωB97X-D functional, which gave the best results compared to the approximate coupled-cluster singles and doubles (CC2) method. A quantitative agreement for both the geometrical parameters and the vibrational frequencies was obtained for the lowest singlet excited state (a ππ* state) of the series of capped peptides. In contrast, only a qualitative agreement was met for the corresponding adiabatic zero-point vibrational energy (ZPVE)-corrected excitation energies. Two composite protocols combining CC2 and DFT/TD-DFT methods were then developed to improve these calculations. Both protocols substantially reduced the error compared to CC2 and experiment, and the best of both even led to results of CC2 quality at a lower cost, thus providing a reliable alternative to this method for very large systems.

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Chemically Accurate Excitation Energies With Small Basis Sets

10.26434/chemrxiv.8427116.v1 ◽

2019 ◽

Author(s):

Emmanuel Giner ◽

Anthony Scemama ◽

Julien Toulouse ◽

Pierre-Francois Loos

Keyword(s):

Excited States ◽

Configuration Interaction ◽

Density Functional ◽

Chem Phys ◽

Basis Set ◽

Basis Sets ◽

Excitation Energies ◽

Functional Correction ◽

The One ◽

Range Density

<p>By combining extrapolated selected configuration interaction (sCI) energies obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) algorithm with the recently proposed short-range density-functional correction for basis-set incompleteness [Giner et al., J. Chem. Phys. 2018, 149, 194301], we show that one can get chemically accurate vertical and adiabatic excitation energies with, typically, augmented double-ζ basis sets. We illustrate the present approach on various types of excited states (valence, Rydberg, and double excitations) in several small organic molecules (methylene, water, ammonia, carbon dimer and ethylene). The present study clearly evidences that special care has to be taken with very diffuse excited states where the present correction does not catch the radial incompleteness of the one-electron basis set.</p>

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Chemically Accurate Excitation Energies With Small Basis Sets

10.26434/chemrxiv.8427116 ◽

2019 ◽

Author(s):

Emmanuel Giner ◽

Anthony Scemama ◽

Julien Toulouse ◽

Pierre-Francois Loos

Keyword(s):

Excited States ◽

Configuration Interaction ◽

Density Functional ◽

Chem Phys ◽

Basis Set ◽

Basis Sets ◽

Excitation Energies ◽

Functional Correction ◽

The One ◽

Range Density

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Exploitation of Baird Aromaticity and Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons

Chemistry ◽

10.3390/chemistry3020038 ◽

2021 ◽

Vol 3 (2) ◽

pp. 532-549

Author(s):

Felix Plasser

Keyword(s):

Polycyclic Aromatic Hydrocarbons ◽

Excited States ◽

Aromatic Hydrocarbons ◽

Density Functional ◽

Materials Science ◽

Chemical Shifts ◽

Qualitative Description ◽

Triplet States ◽

Excitation Energies ◽

Polycyclic Aromatic

Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet states of four biphenylene-derived PAHs finding dramatically different triplet excitation energies for closely related isomeric structures. These differences are rationalised using a qualitative description of Clar sextets and Baird quartets, quantified in terms of nucleus independent chemical shifts, and represented graphically through a recently developed method for visualising chemical shielding tensors (VIST). The results are further interpreted in terms of a 2D rigid rotor model of aromaticity and through an analysis of the natural transition orbitals involved in the triplet excited states showing good consistency between the different viewpoints. We believe that this work constitutes an important step in consolidating these varying viewpoints of electronically excited states.

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Quantum-Chemical Ab Initio Calculations on Inda- and Thallabenzene (C5H5In and C5H5Tl) and their Structural Isomers η5-C5H5In and η5-C5H5Tl

Australian Journal of Chemistry ◽

10.1071/ch17472 ◽

2018 ◽

Vol 71 (3) ◽

pp. 102

Author(s):

Emma Persoon ◽

Yuekui Wang ◽

Gerhard Raabe

Keyword(s):

Ab Initio ◽

Quantum Chemical ◽

Density Functional ◽

Single Point ◽

Normal Modes ◽

Dft Method ◽

Basis Sets ◽

Triplet States ◽

Structural Isomers ◽

Td Dft

Quantum-chemical ab initio, time-independent, as well as time-dependent density functional theory (TD-DFT) calculations were performed on the so far elusive heterocycles inda- and thallabenzene (C5H5In and C5H5Tl), employing several different methods (MP2, CISD, CCSD, CCSD(T), BD, BD(T), QCISD, QCISD(T), CASSCF, DFT/B3LYP), effective core potentials, and different basis sets. While calculations on the MP2 level predict the ground states of the title compounds to be singlets with the first triplet states between 13 and 15 kcal mol−1 higher in energy, single point calculations with the QCISD(T), CCSD(T), and BD(T) methods at CCSD-optimized structures result in energy differences between the singlet and the triplet states in the range between 0.3 and 2.1 kcal mol−1 in favour of the triplet states. According to a CASSCF(8,8) calculation the triplets are also more stable by about 2.5–2.9 kcal mol−1. Calculations were also performed for the C5v-symmetric η5 structural isomers (cyclopentadienylindium, CpIn, and cyclopentadienylthallium, CpTl, Cp = C5H5) of the title compounds. At the highest level of theory employed in this study, C5H5In is between 79 and 88 kcal mol−1 higher in energy than CpIn, while this energy difference is even larger for thallabenzene where C5H5Tl is energetically between 94 and 102 kcal mol−1 above CpTl. In addition we report on the UV/vis spectra calculated with a TD-DFT method as well as on the spectra of the normal modes of C5H5In and C5H5Tl. Both types of spectra might facilitate identification of the title compounds eventually formed in photolysis or pyrolysis experiments.

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Spectroscopic trends in a series of Re(I) α-diimine complexes as a function of the antenna/photoisomerizable ligands: a TD-DFT and MS-CASPT2 study

Canadian Journal of Chemistry ◽

10.1139/cjc-2014-0069 ◽

2014 ◽

Vol 92 (10) ◽

pp. 979-986 ◽

Cited By ~ 11

Author(s):

Megumi Kayanuma ◽

Chantal Daniel ◽

Etienne Gindensperger

Keyword(s):

Excited States ◽

Electronic Structures ◽

Density Functional ◽

Time Dependent ◽

Functional Theory ◽

B3lyp Level ◽

Ligand Charge Transfer ◽

Td Dft ◽

Energy Domain ◽

Diimine Complexes

The absorption spectra of 11 rhenium(I) complexes with photoisomerizable stilbene-like ligands have been investigated by means of density functional theory (DFT). The electronic structures of the ground and excited states were determined for [Re(CO)3(N,N)(L)]+ (N,N = bpy (2,2′-bipyridine), phen (1,10-phenanthroline), Me4phen (3,4,7,8-tetramethyl-1,10-phenanthroline), ph2phen (4,7-diphenyl-1,10-phenanthroline), or Clphen (5-chloro-1,10-phenanthroline); L = bpe (1,2-bis(4-pyrydil)ethylene), stpy (4-styrylpyridine), or CNstpy (4-(4-cyano)styrylpyridine)) at the time–dependent (TD) DFT/CAM-B3LYP level of theory in vacuum and acetonitrile to highlight the effects of both antenna N,N and isomerizable L ligands. The TD-DFT spectra of two representative complexes, namely [Re(CO)3(bpy)(stpy)]+ and [Re(CO)3(phen)(bpe)]+, have been compared with MS-CASPT2 spectra. The TD-DFT spectra obtained in vacuum and acetonitrile agree rather well both with the ab initio and experimental spectra. The absorption spectroscopy of this series of molecules is characterized by the presence of three low-lying metal to ligand charge transfer (MLCT) states absorbing in the visible energy domain. The nature of the isomerizable ligands (bpe, stpy, or CNstpy) and the type of antenna ligands (bpy, phen, and substituted phen) control the degree of mixing between the MLCT and intraligand excited states, their relative energies, as well as their intensities.

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Predicting the UV–vis spectra of oxazine dyes

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.7.56 ◽

2011 ◽

Vol 7 ◽

pp. 432-441 ◽

Cited By ~ 36

Author(s):

Scott Fleming ◽

Andrew Mills ◽

Tell Tuttle

Keyword(s):

Excitation Energy ◽

Density Functional ◽

Polarizable Continuum Model ◽

Implicit Solvent ◽

Continuum Approach ◽

Excitation Energies ◽

Functional Theory ◽

Partial Charges ◽

Td Dft ◽

Polarizable Continuum

In the current work we have investigated the ability of time-dependent density functional theory (TD-DFT) to predict the absorption spectra of a series of oxazine dyes and the effect of solvent on the accuracy of these predictions. Based on the results of this study, it is clear that for the series of oxazine dyes an accurate prediction of the excitation energy requires the inclusion of solvent. Implicit solvent included via a polarizable continuum approach was found to be sufficient in reproducing the excitation energies accurately in the majority of cases. Moreover, we found that the SMD solvent model, which is dependent on the full electron density of the solute without partitioning into partial charges, gave more reliable results for our systems relative to the conductor-like polarizable continuum model (CPCM), as implemented in Gaussian 09. In all cases the inclusion of solvent reduces the error in the predicted excitation energy to <0.3 eV and in the majority of cases to <0.1 eV.

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