Structured phosphorescence

Luminescence studies of DMT in an ethanol glass at 77°K are reported to have shown a highly structured phosphorescent emission with maxima at 391, 404, 418, 432, and 446 nm and a mean... 

Fluorescence was used to investigate the excited-state dynamics of the radical cation of thianthrene (TH ) <2001PCA6594>. The frequencies of the fundamental modes of the molecules of some dioxins in the ground electronic state were also determined by analysis of their fine-structure phosphorescence spectra <19990PS(86)239, 19970PS(83)92, 20000PS(89)42, 20000PS(88)339>. 

The photochemistry of polysilane derivatives may occur also via the triplet state 13, 30), on the basis of the observation of a weak-structured phosphorescence characteristic of a localized excited state for a number of polysilane derivatives. In principle, the halogenated additives could promote intersystem crossing via an intermolecular heavy-atom effect (39). Again, however, why the two structurally similar polysilanes should respond so differently to the presence of the additive is unclear. 

We have studied the thermochromism of fluorescence and show this behavior to be consistent with the rotational isomeric state model previously proposed to explain solution thermochromism in absorption (9,10). Weak, structured phosphorescence is observed from all polymers studied. The contrast between the structured phosphorescence and the narrow fluorescence is interpreted as evidence that the triplet state is the immediate precursor to photochemistry. Finally, the change in the fluorescence character in the aryl series on going from phenyl substitution to naphthyl substitution suggests a change in the nature of the transition from one involving mixed side chain-backbone states in the phenyl case to one which is primarily side chain-like for naphthyl-substituted polysilylenes. 

Fig. 4. Phosphorescence spectra at 77 K of (A) p7 nucleocapsid protein from HIV-1 and (B) the complex of p7 with (dG)g. The structured phosphorescence originates from Trp-37 on the C-terminal zinc finger. Excitation is at 295 nm with 16 nm bandwidth. The solvent is 5 mM phosphate buffer, pH 6.5, containing 20% (v/v) ethylene glycol. The p7 concentration is 0.25 mM in (A). In (B), the p7 concentration is 0.062 mM, and the octanucleotide concentration is 0.13 mM. (From W.-C. Lam and A. H. Maki, unpublished data, 1993.)...

The complex Pt(NH3)2(bpy) also has a tt —> n triplet excited state, which results in the observation of a structured phosphorescence at 488 nm that is closely... 

Characteristic of the delayed emission spectrum is the delayed fluorescence band centered at 3 6 nm and the structured phosphorescence emission between 90 nm and 370 nm. That mobile triplet states and... 

This work reports the use of benzophenone, a very well characterized probe, to study new hosts (i.e., modified cellidoses grafted with alkyl chains bearing 12 carbon atoms) by surface esterification. Laser-induced room temperature luminescence ofair-equilibrated or argon-purged solid powdered samples of benzophenone adsorbed onto the two modified celluloses, which will be named C12-1500 and Cl2-1700, revealed the existence of a vibrational-ly structured phosphorescence emission of benzaphenone in the case where ethanol was used for sample preparation, while a nonstructured emission of... 

Benzo[b]thiophene-2,3-quinone, 5-chloro-oxidation, 4, 824 Benzothiophenes, 4, 863-934 biological activity, 4, 911-913 intramolecular acylation, 4, 761 mass spectrometry, 4, 739 metabolism, 1, 242 phosphorescence, 4, 16 reactivity, 4, 741-861 spectroscopy, 4, 713-740 structure, 4, 713-740 substituents reactivity, 4, 796-839... 

In 1944, Lewis and Kasha (52) identified phosphorescence as a forbidden" transition from an excited triplet state to the ground singlet state and suggested the use of phosphorescence spectra to identify molecules. Since then, phosphorimetry has developed into a popular method of analysis that, when compared with fluorometry, is more sensitive for some organic molecules and often provides complimentary information about structure, reactivity, and environmental conditions (53). 

Cyclodextrins can solubilize hydrophobic molecules in aqueous media through complex formation (5-8). A nonpolar species prefers the protective environment of the CDx cavity to the hulk aqueous solvent. In addition, cyclodextrins create a degree of structural rigidity and molecular organization for the included species. As a result of these characteristics, these macrocycles are used in studies of fluorescence and phosphorescence enhancement (9-11), stereoselective catalysis (.12,13), and reverse-phase chromatographic separations of structurally similar molecules (14,15). These same complexing abilities make cyclodextrins useful in solvent extraction. 

Lu, W., Li, Y, Chan, M.C.W., Che, C.-M., Cheung, K.-K and Zhu, N. (2002) Organic triplet emissions of arylacetylide moieties harnessed through coordination to [Au(PCy3)]. Effect of molecular structure upon photoluminescent properties. Journal of the American Chemical Society, 124,14696-14706 (c) Lu, W., Zhu, N. and Che, C.M. (2003) Polymorphic forms of a gold(I) arylacetylide complex with contrasting phosphorescent characteristics. Journal of the American Chemical Society, 125, 16081—16088 ... 

Thomsons picture of the atom emerged from his work with cathode ray tubes. It was a milestone on the road to understanding atomic structure. But it was not the only major advance to come out of cathode ray experiments. Almost every television set in existence today is a cathode ray tube. The electrons stream from the cathode and are deflected by electromagnetic coils guided by signals from the television station. When an electron hits the televisions screen, which is coated with a phosphorescent material, it produces a dot of color. The dots form the picture you see on the screen. 

Since the phosphorescence emission from (6) (68.8 kcal/mole) is very similar in energy and vibrational structure to benzophenone, and has a short lifetime (0.5 msec), it was proposed that the photorearrangement takes place via the triplet state. A Zimmerman-like mechanism is as follows for the formation of the cyclopropyl ketone (7) from dienone (6) ... 

Photophysical Processes in Dimethyl 4,4 -Biphenyldicarboxy-late (4,4I-BPDC). The ultraviolet absorption spectrum of dimethyl 4,4 -biphenyldicarboxyl ate was examined in both HFIP and 95% ethanol. In each case two distinct absorption maxima were recorded, an intense absorption near 200 nm and a slightly less intense absorption near 280 nm. The corrected fluorescence excitation and emission spectra of 4,4 -BPDC in HFIP at 298°K shows a single broad excitation band centered at 280 nm with a corresponding broad structureless emission band centered at 340 nm. At 77°K, the uncorrected phosphorescence spectra shows a single broad structureless excitation band centered at 298 nm, and a structured emission band having maxima at 472 and 505 nm with a lifetime, t, equal to 1.2 seconds. 

Photophysical Processes in Pi butyl 4,4 -Sulfonyldibenzoate (4,4 -SD). The UV absorption spectra of dibutyl 4,4 -sulfonyl-dibenzoate (4,4 -SD) in both HFIP and 95% ethanol showed similar absorptions. The corrected excitation and emission fluorescence spectra of 4,4 -SD in HFIP at 298°K showed a structured excitation with band maxima at 236, 286, and 294 nm and a structured emission exhibiting band maxima at 322, 372, and 388 nm. The uncorrected excitation and phosphorescence spectra of 4,4 -SD in a 95% ethanol glass at 77°K displayed excitation band maxima at 268, 282, and 292 nm with strong phosphorescence emission with band maxima at 382, 398, and 408 nm with a mean lifetime (t) of 1.2 sec. 

Phosphorescence spectra of DTT and DTP were measured in MeOH/EtOH glass at 77 K. DTT and DTP exhibited phosphorescence with clear vibrational structure. This finding is attributed to the rigid structure caused by the bridging group at the 3,3 positions of 2,2-bisthiophene 84. The triplet energy of DTT and DTP estimated from the 0-0 bands of the phosphorescence spectra are given in Table 9. 

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