A new INDO-type procedure for conjugated non-rogid molecules. II. Extension to electronic spectra and excited-state potential curves

Momicchioli, Fabio; Baraldi, Ivan; Bruni, M.C.

doi:10.1016/0301-0104(83)85359-2

Cited by 76 publications

(35 citation statements)

References 117 publications

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“…We note that the absolute energy of TI (n,n*) is rather underestimated by the calculation with respect to an experimental value of ca 58-60 kcal/mol, which can be derived from the position of the phosphorescence band. The disagreement with the experimental energies could be related to the large deviation of the geometry from planarity, due to the fact that the INDO method fails to account properly for the balance between un (hyperconjugative) and n-n (conjugative) interactions occurring in nonplanar geometries (27). These factors are expected to affect much less the more localized n,n* states, for which the calculated S-T splitting (ca 6.7 kcalfmol) is that normally found in aromatic ketones (15).…”

Section: Photophysical Behaviormentioning

confidence: 95%

Triplet Photoreactivity of the Diaryl Ketone Tiaprofenic Acid and Its Decarboxylated Photoproduct. Photobiological Implications

et al. 1998

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The 2-benzoylthiophene chromophore of the photosensitizing drug tiaprofenic acid and of its decarboxylated derivative is characterized by a unusually high energy gap between the T1 (pi, pi*) and T2 (n, pi*) excited states, which makes this a unique system to study the intrinsic photoreactivity of the two states. Weak fluorescence and phosporescence emission were detected at room temperature. Tiaprofenic acid undergoes photodecarboxylation from the triplet manifold as the main reaction. The photoprocess is temperature dependent with activation energy of 7-10 kcal/mol, close to the energy gap between T1 and T2. The decarboxylated product abstracts hydrogen in type I reactions. The involvement of T2 in the above processes is proposed. Moreover the decarboxylated derivative exhibits reactivity toward phenols, consistent with a participation of the T1 state as electron acceptor. The observed photoprocesses can account for biological photosensitization reactions, like membrane damage and protein modification.

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Section: Photophysical Behaviormentioning

confidence: 95%

Triplet Photoreactivity of the Diaryl Ketone Tiaprofenic Acid and Its Decarboxylated Photoproduct. Photobiological Implications

et al. 1998

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“…Molecular orbital calculations were carried out using the CS-JNDO method described in detail elsewhere. 33 The INDO parameters (screening factors for the resonance integrals and one-center and two-center integrals) were taken from ref 34. The structural parameters of H1T used for the calculations are given in Figure 6.…”

Section: Analysis Of the Excited Statesmentioning

confidence: 99%

Triphenylene Columnar Liquid Crystals: Excited States and Energy Transfer

Markovitsi¹,

Germain²,

Millié³

et al. 1995

J. Phys. Chem.

171

200

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The present paper deals with the photophysical properties of columnar liquid crystals formed by hexakis-(alky1oxy)triphenylenes. Absorption and fluorescence spectra of solutions are analyzed on the basis of quantum chemical calculations performed by the CS-INDO-CI (conformations spectra-intermediate neglect of differential overlap-configuration interaction) m e t h d . the absorption maximum is due to the SO -Sq transition while fluorescence originates from the weak SO -S1 transition. In columnar aggregates, the former transition corresponds to delocalized excited states while the latter corresponds to localized ones; calculation of intermolecular interactions shows that, at the temperature domain of the mesophases, all the molecules have the same excitation energy and, therefore, no spectral diffusion of the fluorescence is expected, in agreement with the time-resolved emission spectra. Excitation transfer is investigated by studying the fluorescence decays of mesophases doped with energy traps. Their analysis is made by means of Monte Carlo simulations considering both intracolumnar and intercolumnar jumps and using four different models for the distance dependence of the hopping probability. The best description is obtained with a model based on the extended dipole approximation and taking into account molecular orientation.

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“…The calculations were performed with the CS-INDO/CI$ (Momicchioli et al, 1983), a quantum mechanical method which has already been success-362 I. BARALDI er al.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Electronic Spectra and Photophysics of Uracil Derivatives*

Baraldi¹,

Bruni²,

Costi³

et al. 1990

Photochem & Photobiology

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The changes that the UV absorption spectrum and the photophysics of uracil undergo under hydrogen substitution or deprotonation, were studied theoretically within the CS-INDO/CI scheme. First of all this method was tested on uracil. It was then used for the calculation of the electronic structure of excited states (Sn, Tn) of a large number of uracil derivatives (1-, 3- and 5-methyluracil; 1,3-, 1,5- and 3,5-dimethyluracil; 5-fluoro- and 5-chlorouracil), including some anions (1- and 3-methyluracil anion). The excited states were obtained in the singly-excited configuration interaction approximation (S-CI) and the correlation effects on (pi pi*) states were studied by including the most important doubly- and triply-excited configurations in the CI. The S-CI wavefunctions were used for the calculation of the most important electronic matrix elements for spin-orbit coupling. The photophysics of these compounds is discussed using Jablonski diagrams.

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A new INDO-type procedure for conjugated non-rogid molecules. II. Extension to electronic spectra and excited-state potential curves

Cited by 76 publications

References 117 publications

Triplet Photoreactivity of the Diaryl Ketone Tiaprofenic Acid and Its Decarboxylated Photoproduct. Photobiological Implications

Triplet Photoreactivity of the Diaryl Ketone Tiaprofenic Acid and Its Decarboxylated Photoproduct. Photobiological Implications

Triphenylene Columnar Liquid Crystals: Excited States and Energy Transfer

Theoretical Study of Electronic Spectra and Photophysics of Uracil Derivatives*

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