Triplet-state energies

The triplet-state energy level of oxytetracycline, the excitation maximum (412 nm), lifetimes of Eu-OxTc (58 p.s) and Eu-OxTc-Cit (158 p.s), were determined. A 25-fold luminescence enhancement at 615 nm occurs upon addition of citrate within a short 5-min incubation time at neutral pH. It s accompanied by a threefold increase of the luminescence decay time. The optimal conditions for determination of OxTc are equal concentrations of Eu(III) and citrate (C = T lO mol-E ), pH 7.2. Eor determination of citrate, the optimal conditions concentrations of Eu(HI) and OxTc are 1 0,5 (Cg = MO Huol-E-i, = 5-10-HuohE-i) at pH 7.2. 

Hall, G. G., Proc. Roy. Soc. [London) A213, 113, The molecular orbital theory of chemical valency. XI. Bond energies, resonance energies and triplet state energies. ... 

Jablonski (48-49) developed a theory in 1935 in which he presented the now standard Jablonski diagram" of singlet and triplet state energy levels that is used to explain excitation and emission processes in luminescence. He also related the fluorescence lifetimes of the perpendicular and parallel polarization components of emission to the fluorophore emission lifetime and rate of rotation. In the same year, Szymanowski (50) measured apparent lifetimes for the perpendicular and parallel polarization components of fluorescein in viscous solutions with a phase fluorometer. It was shown later by Spencer and Weber (51) that phase shift methods do not give correct values for polarized lifetimes because the theory does not include the dependence on modulation frequency. 

Thus, the photo-activity of poly[bis(4-benzoylphenoxy)phosphazene] under illumination could be finely tuned by irradiating the polymer in the presence of variable amount of naphthalene, a typical triplet state energy quencher [474]. The same polymer could be used as polymeric photosensitizer to induce the... 

Rios, A. de O., A. Z. Mercadante, and C. D. Borsarelli. 2007. Triplet state energy of the carotenoid bixin determined by photoacoustic calorimetry. Dyes Pigments 74 561-565. 

Moreover, carotenoids may quench electronically excited states and scavenge free radicals formed in the retina, and therefore protect biomolecules from oxidative damage. Due to the low energy level of the first excited triplet state ( Car), carotenoids (Car) can act as efficient acceptors of triplet state energy from photosensitizers (S) (Equation 15.1), such as all-tra .s-retinal, the photosensitizers of lipofuscin (Rozanowska et al., 1998), or singlet oxygen C02) (Equation 15.2) (Cantrell et al., 2003) ... 

Deactivation of the excited stabilizer molecule in its excited singlet (screening effect) and triplet state (energy transfer). 

Hirota, N. Use of triplet-state energy transfer in obtaining singlet-triplet absorption in organic crystals. J. Chem. Phys. 44, 2199 (1966). 

The value of the triplet state energy of CoPc species is not known. 

Helene110 says that thymidine fluorescence from aqueous solutions at 77°K of a thymidine-adenosine mixture (as well as the identical fluorescence from rigid solutions of G + T, AcC + T or C + T) is owing to a triplet energy transfer to the thymidine moiety. The order of triplet-state energies among the purines and pyrimidines is given as... 

Table 22. Excited State Parameters of the Helicenes. Quantum yield of fluorescence (

Latva, M. Takalo, H. Mukkala, V.- . Matachescu, C. Rodrfguez-Ubis, J.-C. Kankare, J. Correlation between the lowest triplet state energy level of the ligand and lanthanide(III) luminescence quantum yield. J. Luminesc. 1997, 75, 149-169. 

An increase in the ion annihilation exergonicity AG to values comparable to the excited triplet-state energies (AG I LT < 0) opens an additional electron transfer channel (T-route). In the simplest case, only one excited triplet 3 A or 3 D becomes accessible. Triplet emission can be directly observed from the ECL systems involving rare earth and transition metal complexes with allowed (due to extensive spin-orbit coupling) triplet-singlet electronic transition. 

This process depends greatly on the triplet state concentration and becomes important in some flash photolysis experiments. There is an obvious energetic requirement for this process, that the triplet state energy should be at least half that of the singlet state. 

FIGURE 5. 3-21G triplet states energies and related conformations of l,3-dioxon-4-one system. Reprinted with permission from Ref. 128. Copyright (1988) American Chemical Society... 

TDDFT calculations results were consistent with the band shapes of the optical spectra of the parent complexes and are shown in Fig. 14. The calculated optical transitions are shown as bars under the experimental spectra and consist of MLLCT, ligand-to-ligand charge transfer transitions (LLCT), intraligand n - tt transitions (IL), and metal-complex delocalized-charge transfer transitions (MCDCT). Triplet state energies were also calculated based on a3 MLLCT state and correlated with experimental emission spectral results [53]. 

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