Theoretical study of the electronic spectrum of magnesium-porphyrin

Rubio, Mercedes; Roos, Björn O.; Serrano‐Andrés, Luis; Merchán, Manuela

doi:10.1063/1.478624

Cited by 78 publications

(64 citation statements)

References 43 publications

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“…[89] Vertical excitation energies from different electronic-structure methods have also been compared for D 4h -symmetric metalloporphyrins in terms of the Gouterman model. [5] For this type of compound, it was concluded that TDDFT/SAOP, TDDFT/BP86, and MRMP are in better agreement with experimental data than CASPT2(14/16) [90] and TDDFT/B3LYP calculations: CASPT2 underestimates the B band of Mg porphin and B3LYP overestimates the B band of Zn porphin.…”

Section: Theoretical Methodsmentioning

confidence: 60%

Quantum Chemical Description of Absorption Properties and Excited‐State Processes in Photosynthetic Systems

2011

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The theoretical description of the initial steps in photosynthesis has gained increasing importance over the past few years. This is caused by more and more structural data becoming available for light-harvesting complexes and reaction centers which form the basis for atomistic calculations and by the progress made in the development of first-principles methods for excited electronic states of large molecules. In this Review, we discuss the advantages and pitfalls of theoretical methods applicable to photosynthetic pigments. Besides methodological aspects of excited-state electronic-structure methods, studies on chlorophyll-type and carotenoid-like molecules are discussed. We also address the concepts of exciton coupling and excitation-energy transfer (EET) and compare the different theoretical methods for the calculation of EET coupling constants. Applications to photosynthetic light-harvesting complexes and reaction centers based on such models are also analyzed.

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Section: Theoretical Methodsmentioning

confidence: 60%

Quantum Chemical Description of Absorption Properties and Excited‐State Processes in Photosynthetic Systems

2011

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“…All IVO-CASCI and CASSCF calculations are performed using a CAS (16/12), where the first entry of CAS (m/n) denotes the number of active electrons and the second entry indicates the number of active orbitals. The active orbitals used in the IVO-CASCI and CASSCF calculations comprise eight bonding valence π -orbitals (3b 1u , 2b 2g , 2b 3g , and 1a u ) and four anti-bonding valence π * -orbitals (1b 1u ,1b 2g ,1b 3g , and 1a u ), thus having the same designations as that employed by Rubio et al 25 in their (multiconfigurational second-order perturbation theory (CASPT2) based on a CASSCF reference wave function) studies for MgP. The choice of a chemically appropriate and optimal CAS is important for an accurate determination of the minimum energy structures and energetics of molecules.…”

Section: Resultsmentioning

confidence: 98%

Application of an efficient multireference approach to free-base porphin and metalloporphyrins: Ground, excited, and positive ion states

Chaudhuri¹,

Freed²,

Chattopadhyay³

et al. 2011

The Journal of Chemical Physics

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The improved virtual orbital-complete active space configuration interaction (IVO-CASCI) method is applied to determine the geometries of the ground state of free-base porphin and its metal derivatives, magnesium and zinc porphyrins. The vertical excitation energies and ionization potentials are computed at these optimized geometries using an IVO-based version of multireference Möller-Plesset (IVO-MRMP) perturbation theory. The geometries and excitation energies obtained from the IVO-CASCI and IVO-MRMP methods agree well with experiment and with other correlated many-body methods. We also provide the ground state vibrational frequencies for free-base porphin and Mg-porphyrin. All frequencies are real in contrast to self-consistent field treatments which yield an imaginary frequency. Ground state normal mode frequencies (scaled) of free-base porphin and magnesium porphyrin from IVO-CASCI and complete active space self-consistent field methods are quite similar and are consistent with Becke-Slater-Hartree-Fock exchange and Lee-Yang-Parr correlation density functional theory calculations and with experiment. In addition, geometries are determined for low-lying excited state triplets and for positive ion states of the molecules. To our knowledge, no prior experimental and theoretical data are available for these excited state geometries of magnesium and zinc porphyrins. Given that the IVO-CASCI and IVO-MRMP computed geometries and excitation energies agree favorably with experiment and with available theoretical data, our predicted excited state geometries should be equally accurate.

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“…65 This transition is buried under the B band in MgPz, while it results in a distinguishable shoulder, sh 1 , of the B band in NiPz.…”

Section: Excited States and Optical Spectramentioning

confidence: 99%

The Optical Spectra of NiP, NiPz, NiTBP, and NiPc: Electronic Effects ofMeso-tetraaza Substitution and Tetrabenzo Annulation

Rosa¹,

Ricciardi²,

Baerends³

et al. 2001

J. Phys. Chem. A

129

128

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Time-dependent density functional calculations have been performed on the symmetry and spin-allowed E u excited states of the nickel tetrapyrrole series, NiP, NiPz, NiTBP, and NiPc. Optical spectra collected in noncoordinating solvents are presented for NiTBP, for the newly synthesized octaethyl nickel porphyrazine, NiOEPz, and for MgOEPz. The theoretical results prove to agree very well with the experimental data, providing an accurate description of the UV-vis spectra. The effects on the optical spectra of introducing in the basic porphyrinic ring, aza bridges, benzo rings, both aza bridges and benzo rings, and a transition metal are highlighted and interpreted on the basis of the electronic structure changes occurring along the series. The following results were found: (i) The near-degeneracy of the configurations (a 1u e g ) and (a 2u e g ) of the fourorbital model leads to strong mixing in NiP. The resulting low-energy state corresponds to the Q band with low intensity due to opposing transition dipoles of the contributing transitions. In NiTBP, NiPz, and NiPc, the degeneracy is lifted, and the lowest transition becomes increasingly purely (a 1u e g ) with concomitant larger intensities in the Q band, which is most intense in NiPc. (ii) The B band is calculated to correspond in NiP to a strong mixture of the degenerate (a 1u e g ) and (a 2u e g ) configurations with parallel transition dipoles, hence a large intensity. In NiPz and NiPc, the B band can no longer be described in terms of the four-orbital model, it has considerable MLCT character in NiPz and corresponds to a more complicated configuration mixing in NiPc. (iii) Transitions involving metal 3d states, either MLCT or LMCT, influence notably the spectrum to the blue of the B band.

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Theoretical study of the electronic spectrum of magnesium-porphyrin

Cited by 78 publications

References 43 publications

Quantum Chemical Description of Absorption Properties and Excited‐State Processes in Photosynthetic Systems

Quantum Chemical Description of Absorption Properties and Excited‐State Processes in Photosynthetic Systems

Application of an efficient multireference approach to free-base porphin and metalloporphyrins: Ground, excited, and positive ion states

The Optical Spectra of NiP, NiPz, NiTBP, and NiPc: Electronic Effects ofMeso-tetraaza Substitution and Tetrabenzo Annulation

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