Assignment of the Q-Bands of the Chlorophylls: Coherence Loss via Qx − Qy Mixing

Reimers, Jeffrey R.; Cai, Zheng-Li; Kobayashi, Rika; Rätsep, Margus; Freiberg, Arvi; Krausz, Elmars

doi:10.1038/srep02761

Cited by 115 publications

(298 citation statements)

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“…52,53 While it has been shown that internal coordinate system yield better results for the vibronic equations due to the fact that there are less coordinates displaced versus the Cartesian system, some of the same researchers have produced significant work and comparisons in Cartesian coordinates. 54,55 In addition to comparisons between the adiabatic and vertical Hessian. 56 It should be noted that an internal coordinate system is many times preferred, but not as widely available.…”

Section: Theoretical and Computational Methodsmentioning

confidence: 99%

Ground and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis

Theisen

Huang

Fleetham

et al. 2015

The Journal of Chemical Physics

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Articles you may be interested inGround and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis The electronic structure of eight zinc-centered porphyrin macrocyclic molecules are investigated using density functional theory for ground-state properties, time-dependent density functional theory (TDDFT) for excited states, and Franck-Condon (FC) analysis for further characterization of the UV-vis spectrum. Symmetry breaking was utilized to find the lowest energy of the excited states for many states in the spectra. To confirm the theoretical modeling, the spectroscopic result from zinc phthalocyanine (ZnPc) is used to compare to the TDDFT and FC result. After confirmation of the modeling, five more planar molecules are investigated: zinc tetrabenzoporphyrin (ZnTBP), zinc tetrabenzomonoazaporphyrin (ZnTBMAP), zinc tetrabenzocisdiazaporphyrin (ZnTBcisDAP), zinc tetrabenzotransdiazaporphyrin (ZnTBtransDAP), and zinc tetrabenzotriazaporphyrin (ZnTBTrAP). The two latter molecules are then compared to their phenylated sister molecules: zinc monophenyltetrabenzotriazaporphyrin (ZnMPTBTrAP) and zinc diphenyltetrabenzotransdiazaporphyrin (ZnDPTBtransDAP). The spectroscopic results from the synthesis of ZnMPTBTrAP and ZnDPTBtransDAP are then compared to their theoretical models and nonphenylated pairs. While the Franck-Condon results were not as illuminating for every B-band, the Q-band results were successful in all eight molecules, with a considerable amount of spectral analysis in the range of interest between 300 and 750 nm. The π-π * transitions are evident in the results for all of the Q bands, while satellite vibrations are also visible in the spectra. In particular, this investigation finds that, while ZnPc has a D 4h symmetry at ground state, a C 4v symmetry is predicted in the excited-state Q band region. The theoretical results for ZnPc found an excitation energy at the Q-band 0-0 transition of 1.88 eV in vacuum, which is in remarkable agreement with published gas-phase spectroscopy, as well as our own results of ZnPc in solution with Tetrahydrofuran that are provided in this paper. C 2015 AIP Publishing LLC. [http://dx

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Section: Theoretical and Computational Methodsmentioning

confidence: 99%

Ground and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis

Theisen

Huang

Fleetham

et al. 2015

The Journal of Chemical Physics

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“…In the harmonic approximation to the ground-state and excited-state potential energy surfaces, if the form of the normal modes does not change then the bandwidth for photoemission corresponds to that for photoabsorption, a commonly good approximation in molecular spectroscopy but one that can also fail badly, e.g., for chlorophylls. [92][93] In practice, reorganization energies become susceptible to vibronic coupling effects that can dramatically change the shapes of excited-state potentialenergy surfaces. This occurs as the influence of vibronic coupling depends strongly on the energy gaps between excited states, demanding global accuracy across the excited state manifold if computational methods are to satisfactorily predict absorption and emission bandwidths.…”

Section: Widths Of Photoabsorption and Photoluminescence Spectramentioning

confidence: 99%

Understanding and Calibrating Density-Functional-Theory Calculations Describing the Energy and Spectroscopy of Defect Sites in Hexagonal Boron Nitride

Reimers

Ali

Kobayashi

et al. 2018

J. Chem. Theory Comput.

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145

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Defect states in 2D materials present many possible uses but both experimental and computational characterization of their spectroscopic properties is difficult. We provide and compare results from 13 DFT and ab initio computational methods for up to 25 excited states of a paradigm system, the V N C B defect in hexagonal boron nitride (h-BN). Studied include include: (i) potentially catastrophic effects for computational methods arising from the multi-reference nature of the closed-shell and open-shell states of the defect, which intrinsically involves broken chemical bonds, (ii) differing results from DFT and time-dependent DFT (TDDFT) calculations, (iii) comparison of cluster models to periodic-slab models of the defect, (iv) the starkly differing effects of nuclear relaxation on the various electronic states as broken bonds try to heal that control the widths of photoabsorption and photoemission spectra, (v) the effect of zero-point energy and entropy on free-energy differences, (vi) defect-localized and conduction/valence band transition natures, and (vii) strategies needed to ensure that the lowest-energy state of a defect can be computationally identified. Averaged state-energy differences of 0.3 eV are found between CCSD(T) and MRCI energies, with thermal effects on free energies sometimes also being of this order. However, DFT-based methods can perform very poorly. Simple generalized-gradient functionals like PBE fail at the most basic level and should never be applied to defect states. Hybrid functionals like HSE06 work very well for excitations within the triplet manifold of the defect, with an accuracy equivalent to or perhaps exceeding the accuracy of the ab initio methods used. However, HSE06 underestimates triplet state energies by on average 0.7 eV compared to closed-shell singlet states, while open-shell singlet states are predicted to be too low in energy by 1.0 eV. This leads to miss-assignment of the ground state of the V N C B defect. Long-range corrected functionals like CAM-B3LYP are shown to work much better and to represent the current entry level for DFT calculations on defects. As significant differences between cluster and periodic-slab models are also found, the widespread implementation of such functionals in periodic codes is in urgent need.

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“…It can also be extended to multi-mode multi-state problems including modes of different symmetry [27] (e.g., the electrochemical, spin resonance, electronic spectroscopy, vibrational spectroscopy, Stark spectroscopy, etc., of the special-pair radical cation in bacterial photosynthesis can be quantitatively modelled [47,49] in quick time using a 70-mode 4-state model [50], the Q-band spectra of the chlorophyllides can be fitted using a real-time algorithm involving 52 modes and 2 states [55], etc.). However, solution of the problem using Born-Oppenheimer basis functions is intrinsically unstable, requiring vibrational basis sets with dimensions found to scale empirically as conical intersections are approached as This general requirement for the convergence of any numerical calculation of full quantum dynamics performed using the Born-Oppenheimer representation immediately tells that the diagonal correction is globally important.…”

Section: Lmentioning

confidence: 99%

“…Simple models can also be extended to universal quantitative ones provided that full quantum solutions [26,50], sufficient interfering processes [43,[51][52], and motions orthogonal to the reaction coordinate are also included [27,[53][54]. The assignment [55] of the Q-band spectrum of chlorophyll-a, arguably the world's most important chromophore whose properties display a strong pseudo-Jahn-Teller effect, following 50 years of intense debate, provides another example of the power of this approach.…”

Section: Related Contentmentioning

confidence: 99%

Diabatic models with transferrable parameters for generalized chemical reactions

Reimers

McKemmish

McKenzie

et al. 2017

J. Phys.: Conf. Ser.

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Abstract. Diabatic models applied to adiabatic electron-transfer theory yield many equations involving just a few parameters that connect ground-state geometries and vibration frequencies to excited-state transition energies and vibration frequencies to the rate constants for electrontransfer reactions, utilizing properties of the conical-intersection seam linking the ground and excited states through the Pseudo Jahn-Teller effect. We review how such simplicity in basic understanding can also be obtained for general chemical reactions. The key feature that must be recognized is that electron-transfer (or hole transfer) processes typically involve one electron (hole) moving between two orbitals, whereas general reactions typically involve two electrons or even four electrons for processes in aromatic molecules. Each additional moving electron leads to new high-energy but interrelated conical-intersection seams that distort the shape of the critical lowest-energy seam. Recognizing this feature shows how conicalintersection descriptors can be transferred between systems, and how general chemical reactions can be compared using the same set of simple parameters. Mathematical relationships are presented depicting how different conical-intersection seams relate to each other, showing that complex problems can be reduced into an effective interaction between the ground-state and a critical excited state to provide the first semi-quantitative implementation of Shaik's "twin state" concept. Applications are made (i) demonstrating why the chemistry of the firstrow elements is qualitatively so different to that of the second and later rows, (ii) deducing the bond-length alternation in hypothetical cyclohexatriene from the observed UV spectroscopy of benzene, (iii) demonstrating that commonly used procedures for modelling surface hopping based on inclusion of only the first-derivative correction to the Born-Oppenheimer approximation are valid in no region of the chemical parameter space, and (iv), demonstrating the types of chemical reactions that may be suitable for exploitation as a chemical qubit in some quantum information processor. IntroductionThough chemical reactions involve complicated restructuring of the electronic and nuclear configuration and dynamics, it can be useful to use the simplification of envisaging reactions as occurring along a single reaction coordinate. This basic concept forms the conceptual framework of Transition-State Theory and much of modern chemistry. Modern electronic-structure calculation methods can predict wide ranges of properties to within the accuracy of experimental measurements, capturing all chemical and spectroscopic features of the system, but such approaches rarely provide insight into why processes occur and have to be repeated for each small system variation. Diabatic models can be used to interpret these calculations, however, revealing the chemical features controlling the process. Basically, simple forms, called diabatic surfaces, are used to describe the reactants and pro...

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Assignment of the Q-Bands of the Chlorophylls: Coherence Loss via Qx − Qy Mixing

Cited by 115 publications

References 46 publications

Ground and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis

Ground and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis

Understanding and Calibrating Density-Functional-Theory Calculations Describing the Energy and Spectroscopy of Defect Sites in Hexagonal Boron Nitride

Diabatic models with transferrable parameters for generalized chemical reactions

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