Phosphorescence spectrum and mechanisms of benzaldehyde in methyl-cyclohexane at 4.2°K

Olmsted, J.; El‐Sayed, Mostafa A.

doi:10.1016/0022-2852(71)90009-9

Cited by 39 publications

(9 citation statements)

References 23 publications

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“…For BA, the vertical contributions are responsible for 65% of the spectrum. This contribution is smaller than that estimated by Olmsted and El-Sayed [4], who gave 93%. For MeBA at the global minimum, the vertical contribution of 49% is still significant.…”

Section: Phosphorescence Of the Ba Derivativescontrasting

confidence: 63%

“…Olmsted and El-Sayed proposed that BA phosphorescence could be analyzed using a C−O diatomic model [4]. If we follow their suggestion and rotate the z-axis to coincide with the carbonyl bond direction (as also done in Refs.…”

Section: Origins Of the Fast And Slow Phosphorescencementioning

confidence: 91%

“…While emission from 3 n* is found within 1 ms, from 3 *, it may take over 100 ms. This difference between phosphorescence lifetimes is often experimentally employed to assign the triplet state character [3], and several papers discuss when this assignment may break due to vibronic couplings [4,5]. Moreover, it is at the basis of strategies for designing efficient pure organic room-temperature phosphorescent chromophores [6].…”

Section: Introductionmentioning

confidence: 99%

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On the short and long phosphorescence lifetimes of aromatic carbonyls

Mukherjee

Kar

Bhati

et al. 2023

Preprint

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This work applies theoretical and computational methods to investigate the relationship between phosphorescence lifetime and the electronic character of the lowest triplet state of aromatic carbonyls. A formal analysis of the spin-perturbed wave functions shows that phosphorescence is due to a direct spin-orbit coupling mechanism modulated by permanent dipoles when the T1 minimum is 3nπ*. If the minimum is a totally symmetric 3ππ*, phosphorescence is due to an indirect spin-orbit coupling mechanism involving transition dipole moments with other excited states. The magnitude difference between permanent and transition dipoles leads to a much faster 3nπ* phosphoresce than 3ππ* if vibronic coupling effects are not considered. These predictions were verified with phosphorescence lifetime simulations of benzaldehyde and its three derivatives in the gas phase employing a vertical approximation as well as the nuclear ensemble approach. Both simulation methods deliver good results for molecules with a 3nπ* T1 minimum. Nevertheless, vertical simulations fail for those molecules with a 3ππ* T1 minimum due to the overwhelming importance of vibronic couplings.

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Section: Phosphorescence Of the Ba Derivativescontrasting

confidence: 63%

Section: Origins Of the Fast And Slow Phosphorescencementioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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On the short and long phosphorescence lifetimes of aromatic carbonyls

Mukherjee

Kar

Bhati

et al. 2023

Preprint

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“…This is consistent with the observation that the π*←n spectra of carbonyl compounds are dominated by progressions in the CO stretching frequency that reflect substantial changes in the CO bond length due to its weakening. Olmsted and El-Sayed estimated an increase in the CO bond length of 0.076 Å from their intensity measurements of the phosphorescence emission of benzaldehyde in methylcyclohexane at 4.2 K. Thakur estimated a CO bond length of 1.311 Å from his determination of the T(nπ*) state rotational constants. He assumed that benzaldehyde is planar in the excited state and that it has 1 B 2u benzene's ring structural parameters and a Ph−CHO bond length of 1.380 Å.…”

Section: Theoretical Sectionmentioning

confidence: 99%

Theoretical Calculations on Excited Electronic States of Benzaldehyde and Observation of the S₂←S₀ Jet-Cooled Spectrum

and

Reilly

1996

J. Phys. Chem.

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The S2(ππ*)←S0 spectrum of jet-cooled benzaldehyde has been recorded by laser ionization. The band has been located at 35 191 cm-1. Ten fundamental vibrations have been assigned following a vibrational analysis assisted by theoretical calculations. Ab initio molecular orbital methods have been used to examine the electronically excited states of benzaldehyde. On π*←n excitation the primary geometric distortions are in the formyl group, while on π*←π excitation these are mainly in the aromatic ring. Vibrational frequencies were found to be in reasonable agreement with the experimental data for the states studied (S0, S1(nπ*), S2(ππ*), and T(nπ*)), and the calculations provided a useful guide in assigning the observed excited state fundamentals.

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“…3,8−10,16,18,23−25 Both ISC and IC contribute to the highly phosphorescent character of benzaldehyde by forcing the molecule into the T 1 state and therefore must be addressed. First, regarding ISC, several authors 1,9,23,26,27 have shown qualitatively the fast ISC between S 1 and T 2 (π−π*) states following El-Sayed rules. 28 To our knowledge, however, quantitative estimates of the ISC rate constant have not been calculated using modern electronic structure theory.…”

Section: Introductionmentioning

confidence: 99%

Electronic Relaxation in Benzaldehyde Evaluated via TD-DFT and Localized Diabatization: Intersystem Crossings, Conical Intersections, and Phosphorescence

Subotnik

2013

J. Phys. Chem. C

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The photophysics of benzaldehyde are analyzed through the lens of TD-DFT adiabatic excited states and Boys or Edmiston−Ruedenberg localized diabatic states. We predict rate constants for two processes in excited benzaldehyde: (i) the intersystem crossing from S 1 → T 2 and (ii) the phosphorescence from T 1 → S 0 . We also study (iii) the conical intersection between T 2 and T 1 that is putatively responsible for an ultrafast internal conversion process, T 2 → T 1 . In agreement with Ohmori et al. (J. Phys. Chem. 1988, 92 (5), 1086−1093), our results suggest that the S 1 → T 2 intersystem crossing in benzaldehyde is rapid not only because of a large spin−orbit matrix element (i.e., El-Sayed's rule) but also because of a fortuitously small energy barrier. Furthermore, when studying the T 2 → T 1 internal conversion, we find that both Boys and Edmiston−Ruedenberg localization give remarkably stable and accurate diabatic states which will be useful for ongoing studies of dynamics near conical intersections. To our knowledge, this is the first example whereby localized diabatization techniques have been tested and have successfully recovered the topology of a conical intersection.

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Phosphorescence spectrum and mechanisms of benzaldehyde in methyl-cyclohexane at 4.2°K

Cited by 39 publications

References 23 publications

On the short and long phosphorescence lifetimes of aromatic carbonyls

On the short and long phosphorescence lifetimes of aromatic carbonyls

Theoretical Calculations on Excited Electronic States of Benzaldehyde and Observation of the S₂←S₀ Jet-Cooled Spectrum

Electronic Relaxation in Benzaldehyde Evaluated via TD-DFT and Localized Diabatization: Intersystem Crossings, Conical Intersections, and Phosphorescence

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Phosphorescence spectrum and mechanisms of benzaldehyde in methyl-cyclohexane at 4.2°K

Cited by 39 publications

References 23 publications

On the short and long phosphorescence lifetimes of aromatic carbonyls

On the short and long phosphorescence lifetimes of aromatic carbonyls

Theoretical Calculations on Excited Electronic States of Benzaldehyde and Observation of the S2←S0 Jet-Cooled Spectrum

Electronic Relaxation in Benzaldehyde Evaluated via TD-DFT and Localized Diabatization: Intersystem Crossings, Conical Intersections, and Phosphorescence

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Theoretical Calculations on Excited Electronic States of Benzaldehyde and Observation of the S₂←S₀ Jet-Cooled Spectrum