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 o SCF-CI calculation on free base porphin and chlorin; theoretical analysis on intensities of the absorption spectra

Nagashima, Umpei; Takada, Toshikazu; Ohno, Kimio

doi:10.1063/1.451773

Cited by 106 publications

(79 citation statements)

References 16 publications

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“…In addition, the Q y and Soret bands are somewhat blue-shifted [32,33]. Table 2 presents the DFT/MRCI, SAC-CI [15], MRMP [13], and experimental [32,34] data for the excited states of CH 2 and BH 2 . Both the excitation energies, oscillator strengths, and the experimental observed red (Q x ) and blue shift (Q y , B), respectively, are reproduced by our calculations.…”

Section: Hydroporphyrinsmentioning

confidence: 98%

DFT/MRCI calculations on the excited states of porphyrin, hydroporphyrins, tetrazaporphyrins and metalloporphyrins

Parusel

2001

J. Porphyrins Phthalocyanines

108

105

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A combination of density functional theory and multi-reference configuration interaction methods (DFT/MRCI) has been applied to the calculation of electronic absorption spectra in a series of porphyrin-type molecules. The calculated excitation energies and oscillator strengths for free-base porphyrin (PH 2 ) are in excellent agreement with experiment for both lower and higher excited states which are characterized by a significant contribution of double excitations (b20%). The 4 1 B 2u , 4 1 B 3u , and 5 1 B 2u states are assigned to the L-band and the 7 1 B 3u state to the M-band. The results for the hydroporphyrins chlorin (CH 2 ) and bacteriochlorin (BH 2 ) are in agreement with the experimentally observed increase in intensity for the Q-bands relative to PH 2 . For BH 2 we predict a red shift of the Q x -band (0.2 eV) and a blue shift of the B-band (0.5-0.7 eV) in comparison to both PH 2 and CH 2 . For porphyrazine (PzH 2 ) and the commercial pigment phthalocyanine (PcH 2 ) the calculated oscillator strengths of the Qand B-bands are of comparable size explaining the intense color of PcH 2 . For the metalloporphyrins with magnesium (PMg) and zinc (PZn), the x-and y-polarized components of the Q-and B-bands collapse, due to the higher D 4h symmetry of the molecules. The calculations reproduce the slight, experimentally observed increase in the oscillator strength of the Q-band and the decrease for the B-band. These effects are ascribed to the electropositive nature of the metals relative to hydrogen. Except for the Q-bands, which are adequately described by the 'four-orbital model,' it is essential to account for excitations outside the four frontier orbitals as well as double and triple excitations for accurate reproduction of experimental data. We compare our results both with experiment and, where available, recent first-principle SAC-CI, MRMP, and TDDFT calculations.

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Section: Hydroporphyrinsmentioning

confidence: 98%

DFT/MRCI calculations on the excited states of porphyrin, hydroporphyrins, tetrazaporphyrins and metalloporphyrins

Parusel

2001

J. Porphyrins Phthalocyanines

108

105

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“…We employed the molecular structure geometry illustrated in Figure 1, which is the same as the geometry employed by Nagashima et al [9]. The geometrical parameters for the skeleton were based on the X-ray diffraction data obtained by Webb and Tleischer [14], and a few adjustments were made to obtain the DZh symmetry.…”

Section: Basis Set and Molecular Structurementioning

confidence: 99%

“…They also showed the existence of a very lowlying triplet state. Nagashima et al carried out CI calculations including single and double excitations of T electrons on free-base porphin and chlorin using a minimal basis set [9]. The excitation energies and oscillator strengths were calculated.…”

Section: Introductionmentioning

confidence: 99%

Ab initio CI calculations on free‐base porphin

Yamamoto

Noro

Ohno

1992

Int J of Quantum Chemistry

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Ab initio configuration interaction (CI) calculations were carried out on low-lying singlet and triplet T-T* states and ionized states of free-base porphin. We take into account single and double excitations from u and T electrons in the CI calculations. The composite natural orbitals were employed in order to reduce the size of orbital set to be used in the CI. The calculated excitation energies were in good agreement with experimental values. The use of split-valence-type basis and the inclusion of correlation effects of u electrons were proved to be important to describe the low-lying T-T* states, especially the Soret band.

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“…Four electronic transitions are expected, all of them active in one-photon spectroscopy, the two at lower energy denoted Q x , Q y while the two higher B x , B y coalesce in a single band (see Figure 48). A quantitative treatment of the vertical excitation energies for the three molecules can only be performed with ab initio calculation methods [297][298][299][300][301][302][303]. The results from three recent calculations relative to porphyrin and presented in Table 13 differ from experiment [299,304] by no more than 0.2 -0.3 eV not only for the Q x , Q y and B x , B y pairs but also for the weak transitions, usually denoted N x , N y and L y , and observed at higher energies with respect to the Soret band.…”

Section: Porphyrinsmentioning

confidence: 99%

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Gellini

Salvi

2010

Symmetry

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The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, cyclobutadiene and cyclooctatetraene. Pentalene, formally derived from cyclooctatetraene by cross linking, is also considered as a typical antiaromatic system. The main interest is concerned with [n]annulenes and model [n]annulene molecular systems, n ranging from 10 to 18. The rich variety of conformational and configurational isomers and of dynamical processes among them is described. Specific attention is devoted to bridged [10]-and [14]annulenes in the ground and lowest excited states as well as to s-indacene and biphenylene. Experimental data obtained from vibrational and electronic spectroscopies are discussed and compared with ab initio calculation results. Finally, porphyrin, tetraoxaporphyrin dication and diprotonated porphyrin are presented as annulene structures adopting planar/non-planar geometries depending on the steric hindrance in the inner macrocycle ring. Radiative and non-radiative relaxation processes from excited state levels have been observed by means of time-resolved fluorescence and femtosecond transient absorption spectroscopy. A short account is also given of porphycene, the structural isomer of porphyrin, and of porphycene properties.

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A b i n i t i o SCF-CI calculation on free base porphin and chlorin; theoretical analysis on intensities of the absorption spectra

Cited by 106 publications

References 16 publications

DFT/MRCI calculations on the excited states of porphyrin, hydroporphyrins, tetrazaporphyrins and metalloporphyrins

DFT/MRCI calculations on the excited states of porphyrin, hydroporphyrins, tetrazaporphyrins and metalloporphyrins

Ab initio CI calculations on free‐base porphin

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

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