On the interpretation of the external heavy atom effect on singlet-triplet transitions

Minaev, B. F.; Knuts, Sören; Ågren, Hans

doi:10.1016/0301-0104(94)85010-0

Cited by 56 publications

(31 citation statements)

References 28 publications

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“…In crystal, it was found that the Br atom was located close to the intermolecular carbazole moiety, forming a strong halogen bonding C─Br···π with a short distance of 3.461 Å, as shown in Figure b. We then speculated that the efficient RTP was mainly triggered by the external heavy atom effect that is effective within a short distance (less than 4.5 Å) . Further theoretical calculations indicated that the large SOC values of S 1 → T m are caused by the external heavy atom effect, while the SOC value of T 1 → S 0 is insensitive to both the internal and external heavy atom effects, which are in accordance with the phosphorescence efficiency and lifetime.…”

Section: Viewpoints On Organic Rtp Materialsmentioning

confidence: 91%

Room‐Temperature Phosphorescence in Metal‐Free Organic Materials

et al. 2019

Annalen der Physik

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Purely organic materials with room-temperature phosphorescence (RTP) have attracted a growing interest for their potential applications in biological imaging, digital encryption, optoelectronic devices, and so on. To date, many strategies have succeeded in designing efficient organic RTP materials by overcoming the spin-forbidden transition between singlet and triplet states. However, the underlying mechanisms of RTP still remain ambiguous. Such spin prohibition in phosphorescence are clarified, herein, from the perspective of perturbation theory, helping to understand the intrinsic relationship among various phosphorescence parameters, like phosphorescence efficiency, lifetime, intersystem crossing rate, as well as radiative and nonradiative rates. Taking into consideration the recent progress in organic RTP materials, these factors are further illustrated by a selection of the most relevant molecules. In addition, some novel RTP phenomena are also reviewed, thus providing an excellent guideline to constructing efficient RTP materials.

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Section: Viewpoints On Organic Rtp Materialsmentioning

confidence: 91%

Room‐Temperature Phosphorescence in Metal‐Free Organic Materials

et al. 2019

Annalen der Physik

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“…[53,54] However, fluorine is also known to diminish the S 0 Ǟ T 1 transition dipole moment by destroying the balance of different S-S and T-T contributions. [55] In magnesium tetraphenylporphines, it has been proposed that the presence of a few fluorine substitutions on the phenyl rings could enhance the mixing between the triplet states, thereby resulting in blueshifted phosphorescence wavelength and longer lifetime. [56] The bromine 4.8 ϫ 10 [a] High-temperature limit of k in THF.…”

Section: Phosphorescence Wavelength and Lifetimementioning

confidence: 99%

Theoretical Study of Phosphorescence of Iridium Complexes with Fluorine‐Substituted Phenylpyridine Ligands

Minaev

Ågren

et al. 2011

Eur J Inorg Chem

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Time-dependent density functional theory (TD-DFT) with linear and quadratic response approaches was applied to calculate absorption and luminescence spectra of a number of facial and meridional iridium complexes with fluorine-substituted phenylpyridine (F n ppy) ligands. The absorption and luminescence spectra were studied to simulate the photophysical properties of electroluminescent devices fabricated on the basis of these iridium complexes used to increase spin-orbit coupling and the triplet-state blue emission of the corre-

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“…This may occur either by interaction with paramagnetic quenchers, or by quenchers with strong intramolecular spin-orbit coupling, the so-called heavy-atom quenchers. According to Minaev et al, 6 in the last case, the off-resonance quencher promotes intersystem crossing by back-charge transfer. In a study of the fluorescence quenching of several aromatic compounds by the paramagnetic O 2 molecule, and where off-resonance enhanced intersystem crossing is probably operative, Camyshan et al 7 found values of L between 1 and 2 Å.…”

Section: Introductionmentioning

confidence: 99%

“…Finally, for the external heavy-atom effect, values of L similar to those of the other mechanisms are expected. An estimate of L for this effect can be made on the basis of the already mentioned theoretical work by Minaev et al, 6 where from the computed distance dependence of the radiative constant for T 1 →S 0 in ethylene in the presence of Br Ϫ one obtains an exponential dependence with Lϭ0.94 Å. In studies of the quenching of carbazole 8 and phenanthrene 9 fluorescence by iodide, Najbar et al report estimated values of L of 1.3 and 1.8 Å, respectively.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence quenching with exponential distance dependence: Application to the external heavy-atom effect

Rae¹,

Fedorov²,

Berberan‐Santos³

2003

The Journal of Chemical Physics

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A model for fluorescence quenching with exponential distance dependence is developed and applied to external heavy-atom quenching. The systems studied are C 70-bromobenzene and phenanthrene-iodide, in liquid solutions at room temperature and in rigid glasses at 77 K. The predicted parameter correlation is observed in the two systems, which correspond to two extreme and opposite situations, strong and weak quenching. A detailed analysis of the fitted parameters allows the determination of the effective Bohr radii L and of the intrinsic unimolecular rate constants for quenching at contact, k 0. The unusually high value of L for the C 70-bromobenzene pair is tentatively attributed to the extended size of the external part of the orbitals of the fullerene. The room temperature quenching rate constant computed with the determined low-temperature parameters is shown to be in good agreement with the experimental one for both systems studied.

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On the interpretation of the external heavy atom effect on singlet-triplet transitions

Cited by 56 publications

References 28 publications

Room‐Temperature Phosphorescence in Metal‐Free Organic Materials

Room‐Temperature Phosphorescence in Metal‐Free Organic Materials

Theoretical Study of Phosphorescence of Iridium Complexes with Fluorine‐Substituted Phenylpyridine Ligands

Fluorescence quenching with exponential distance dependence: Application to the external heavy-atom effect

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