Near-infrared phosphorescence emission of compounds with low-lying triplet states

1989 ◽  
Vol 159 (1) ◽  
pp. 103-108 ◽  
Author(s):  
A. Völcker ◽  
H.-J. Adick ◽  
R. Schmidt ◽  
H.-D. Brauer
Keyword(s):  
Near Infrared ◽  
Triplet States ◽  
Phosphorescence Emission

The photochemical reactivity of some benzoylthiophenes. IV. The effect of an adjacent methyl group on the excited state reactivity of 3-benzoylthiophene

1978 ◽  
Vol 56 (15) ◽  
pp. 1970-1984 ◽  
Author(s):  
D. R. Arnold ◽  
C. P. Hadjiantoniou
Keyword(s):  
Hydrogen Abstraction ◽  
Thiophene Ring ◽  
Emission Spectra ◽  
Photochemical Reactions ◽  
Triplet States ◽  
Photochemical Reactivity ◽  
Methyl Group ◽  
State Diagrams ◽  
Phosphorescence Emission ◽  
Intramolecular Hydrogen

The electronic absorption and phosphorescence emission spectra and the photochemical reactivity of several methyl-3-benzoylthiophenes (2- and 4-methyl-3-benzoylthiophene (1, 2), 2,5-dimethyl-3-benzoylthiophene (3), and 3-(2-methylbenzoyl)thiophene (4)) have been studied. Partial state diagrams have been constructed. The lowest energy absorption in hexane solution in every case is the carbonyl n → π* transition. The two lowest triplet states of these ketones are close in energy and, in fact, the nature of the emitting triplet (n,π* or π,π*) depends upon the position of methyl substitution and upon the solvent. The photochemical reactions studied include intramolecular hydrogen abstraction (revealed by deuterium exchange in the adjacent methyl group upon irradiation in perdeuteriomethanol solution), photocycloaddition of dimethyl acetylenedicarboxylate to the thiophene ring, and photocycloaddition of isobutylene to the carbonyl group. Generalizations, potentially useful for predicting photochemical reactivity of these and other aromatic ketones are summarized.

From elementary reactions to chemical relevance in the photodynamic therapy of cancer

2013 ◽  
Vol 85 (7) ◽  
pp. 1389-1403 ◽  
Author(s):  
Luis G. Arnaut ◽  
Sebastião J. Formosinho
Keyword(s):  
Photodynamic Therapy ◽  
Theoretical Prediction ◽  
Near Infrared ◽  
Chemical Processes ◽  
Triplet States ◽  
Biological Screening ◽  
Elementary Reactions ◽  
Photodynamic Therapy Of Cancer ◽  
Intense Absorption ◽  
High Yields

Theories of radiationless conversions and of chemical processes were employed to design better photosensitizers for photodynamic therapy (PDT). In addition to photostability and intense absorption in the near infrared, these photosensitizers were required to generate high yields of long-lived triplet states that could efficiently transfer their energy, or an electron, to molecular oxygen. The guidance provided by the theories was combined with the ability to synthesize large quantities of pure photosensitizers and with the biological screening of graded hydrophilicities/lipophilicities. The theoretical prediction that halogenated sulfonamide tetraphenylbacteriochlorins could satisfy all the criteria for ideal PDT photosensitizers was verified experimentally.

scholarly journals Recent Advances on Metal-Based Near-Infrared and Infrared Emitting OLEDs

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1412 ◽  
Author(s):  
Malika Ibrahim-Ouali ◽  
Frédéric Dumur
Keyword(s):  
Metal Complexes ◽  
Optical Communication ◽  
Near Infrared ◽  
Infrared Region ◽  
Infrared Emission ◽  
Organic Light Emitting Diodes ◽  
Triplet States ◽  
Light Emitting ◽  
The Past ◽  
Organic Light

During the past decades, the development of emissive materials for organic light-emitting diodes (OLEDs) in infrared region has focused the interest of numerous research groups as these devices can find interest in applications ranging from optical communication to defense. To date, metal complexes have been most widely studied to elaborate near-infrared (NIR) emitters due to their low energy emissive triplet states and their facile access. In this review, an overview of the different metal complexes used in OLEDs and enabling to get an infrared emission is provided.

Oxygen-Enhanced Upconversion of near Infrared Light from Below the Silicon Band Gap

2019 ◽  
Author(s):  
Timothy Schmidt ◽  
Elham Gholizadeh ◽  
Shyamal Prasad ◽  
Zhi Li Teh ◽  
Thilini Ishwara ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Band Gap ◽  
Near Infrared ◽  
Infrared Light ◽  
Triplet States ◽  
Near Infrared Light ◽  
Semiconductor Nanocrystal ◽  
Photochemical Processes

<div>Here we demonstrate an upconversion composition using semiconductor nanocrystal sensitizers that employs molecular triplet states below the singlet oxygen energy. We show that, contrary to the usual expectation, the admission of oxygen enhances the intensity of upconverted light and significantly speeds up the photochemical processes involved. Further, we demonstrate photochemical upconversion from below the silicon band gap in the presence of oxygen.</div>

Light-induced TPP photoproduct formation in chloroform and protective role of lipids

2010 ◽  
Vol 14 (11) ◽  
pp. 962-967 ◽  
Author(s):  
Roman Dĕdic ◽  
Alexander Molnár ◽  
Antonín Svoboda ◽  
Jan Hála
Keyword(s):  
Singlet Oxygen ◽  
Near Infrared ◽  
Excitation Energy Transfer ◽  
Protective Role ◽  
Triplet States ◽  
Lipid Concentration ◽  
Oxygen Kinetics ◽  
Wide Range ◽  
Lipid Sample ◽  
Single Exponential

In this contribution, the influence of lipids on excitation energy transfer from lipophilic photosensitizer tetraphenylporphyrin to oxygen was investigated in chloroform solutions of phosphatidylcholine as well as in bulk lipid. The excited states kinetics were examined in a wide range of lipid concentrations (from zero to the saturated concentration) by direct time- and spectral-resolved detection of weak near infrared phosphorescence of the photosensitizer (around 840 nm) and singlet oxygen (about 1278 nm). While photosensitizer triplet kinetics follows single-exponential decay with lifetime of 0.52 μs in pure chloroform, two distinct components with lifetimes of approximately 0.4 and 1 μs appear after phosphatidylcholine addition. Both the lifetimes exhibit shortening tendency with increasing lipid concentration. Relative weights of the two components depend on the lipid concentration. Singlet oxygen kinetics exhibit single-exponential rise with lifetimes roughly corresponding to the shorter components of photosensitizer decays while their decays require two exponentials. The lifetime of the longer component decreases with increasing concentration of lipid from (77.6 ± 1.3) μ s at pure chloroform to (14.3 ± 1.1) μ s at the saturated lipid concentration. The time-constants obtained in bulk lipid sample follow the above-mentioned trends. Tetraphenylporphyrin photoproduct formation under pulsed excitation in chloroform solutions was demonstrated. The quantum yield of singlet oxygen production of the photoproduct is lower than that of the tetraphenylporphyrin. It was shown that lipids prevent the singlet-oxygen mediated formation of TPP photoproduct, probably by efficient quenching of singlet oxygen. This quenching is justified by shortening of the longer component of singlet oxygen luminescence decays with increasing concentration of the lipid. Moreover, the lipids also quench triplet states of the photosensitizer.

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