Fluorescence spectrum, anthracene

Figure 28.15 a, Chemiluminescence spectrum obtained from electrolysis of a DMF solution containing 1 mM fluoranthene and 1 mAf 10-MP. Alternating steps at-1.75 V and +0.88 V vs. SCE were used, b, Chemiluminescence spectrum under the same conditions, but with 1 mM anthracene added. Inset shows anthracene fluorescence spectrum for a 10-5 M DMF solution. Reabsorption reduces the 0,0 intensity in b. [From Ref. 99, adapted with permission.]... 

In the presence of anthracene (which has an energetically lower triplet state than fluoranthene or 10-methyl-phenothiazine), the ECL emission is shifted from the broad maximum at ca. 450 nm to the characteristic anthracene fluorescence spectrum with the three maxima at 390, 410 and 445 nm. 

In 1967 spraying with a solution of paraffin wax allowed the recording of the fluorescence spectrum of anthracene directly on the TLC plate without any difficulties [228]. Hellmann too was able to stabilize emissions by the addition of 2% paraffin to the solvent [229]. Low concentrations evidently serve primarily to stabilize the fluorescence — this stabilization concentration extends up to ca... 

The fluorescence spectrum of dibenz[7>,/]oxepin shows that this molecule adopts a planar structure in the excited state whereas the ground state has bent geometry as expected.19 The emission spectrum is similar to that of anthracene. 

A second vital observation was made when Mayneord, a physicist, joined in the research effort and decided to examine the conspicuous fluorescence of the many carcinogenic distillates present in Kennaway s laboratory. He found that most of the carcinogenic tars exhibited a common fluorescence spectrum (X 400, 418 and 440 nm) but, in subsequent studies with Hieger, none of the hydrocarbons available at that time exhibited these spectral characteristics (7 ). The spectrum of benz[a]anthracene was found to be similar to, but of longer wavelength than, that of the carcinogenic preparations but this similarity directed Kennaway s attention to Clar s report of the synthesis of dibenz[a hjanthracene (10). Tumors were obtained when this hydrocarbon was repeatedly painted on to mice and thus it was established that the properties necessary to elicit tumors in animals were contained within the structure of a single pure chemical compound (11). 

The absorption spectrum shows a vibrational structure characteristic of the Si state whereas the fluorescence spectrum shows a vibrational structure characteristic of the S0 state of anthracene. 

Figure 4.2 Absorption spectrum (continuous line) and fluorescence spectrum (dashed line) of anthracene in benzene...

Fig. 3.5. Fluorescence spectrum of benz[a]anthracene in n-heptane liquid solution at 300 K (top) and in n-heptane frozen solution at 15 l< (bottom). Concentration ...

The bisanthraceno-crown ether E-l (Figure 10.26) exhibits a fluorescence spectrum composed of the characteristic monomer and excimer bands. Gradual addition of sodium perchlorate to a solution in methanol induces a decrease in the monomer band and an increase in the excimer band. Complexation is indeed expected to bring closer together the two anthracene units, which favors excimer formation. A 2 1 (metabligand) complex is formed with Na+ in methanol and acetonitrile with a positive cooperative effect (see Appendix B). Interestingly, the overall stability constant obtained from absorption data was found to be lower than that... 

Chandross, Longworth, and Visco126 have reported the observation of long-wave structureless emission bands in the vicinity of the electrodes during the ac electrolysis of anthracene, phenanthrene, perylene, and 3,4-benzpyrene in polar solvents such as acetonitrile and dimethylformamide the similarity between the perylene band and the crystal fluorescence spectrum prompted the assignment of these bands to excimer fluorescence originating in the process... 

Fig. 17. Delayed fluorescence spectrum of 5 X 10-63/ anthracene in ethanol.84 Half-bandwidth of analyzing monochromator was 0.05 ju-1 at 2.5 n K Intensity of exciting light was approximately 1.4 X 10 einstein cm. a sec.-1 at 2.73m-1 (366 mju). (1) Normal fluorescence spectrum (distorted by self-absorption). (2) Delayed emission spectrum at sensitivity 260 times greater than for curve 1. (3) Spectral sensitivity of instrument (units of quanta and frequency).

Fig. 7. The fluorescence spectrum of anthracene vapor (from J. Haebig, Ph.D. Thesis, University of Chicago (1966)). (—) Excitation at 3650 A (first absorption...

A fluorescence spectrum is characteristic of a given compound. It is observed as a result of radiative emission of the energy absorbed by the molecule. The observed spectrum does not depend on the wavelength of the exciting light, except that the spectrum will be more intense if irradiation occurs at the absorption maximum. The spectral intensity is called the quantum efficiency and is usually abbreviated as . The quantum yield or quantum efficiency, d>, which is solvent dependent, is the ratio Approximate values of quantum efficiencies are as follows naphthalene, 0.1 anthracene, 0.3 indole, 0.5 and fluorescein, 0.9. 

The process of fast and reversible pH-driven metal inclusion-extrusion can be easily followed, in the case of 15b derivative, through the emission of the anthracene fragment covalently linked to the macrocycle. Figme 3 shows the fluorescence intensity, Ip, versus pH profile obtained in the course of spectrofluorimetric titration experiments. First, when an aqueous MeCN solution of 15b (H2L), containing excess acid is titrated with standard base, the typical anthracene emission spectrum is not modified over the pH range 3 to 10.5. If the titration experiment is carried out in presence of 1 equivalent of Cu at pH = 3.6, Ip begins to decrease sigmoidally. 

Figure 6. (a) Fluorescence spectrum of a mixture of naphthalene, phenanthrene, anthracene, perylene, ana tetracene (Xga. = 258 nm). (b) Synchronous signal (AX = 3 nm) of the same mixture. 

Figure 5. MI fluorescence spectrum of LC Fraction V from Synthoil at two excitation wavelengths. BaA = benz[a]anthracene C = chrysene U = unknown P = pyrene (artifact not present in fraction).

---