Fluoranthene excited

If chemiluminescence is to occur, a critical electron-transfer enthalpy value must be exceeded. This value is similar to the energy of the lowest excited triplet state, as was found in the case of fluoranthene 150>, for example. 

Chemically inert triplet quenchers e.g. trans-stilbene, anthracene, or pyrene, suppress the characteristic chemiluminescence of radical-ion recombination. When these quenchers are capable of fluorescence, as are anthracene and pyrene, the energy of the radical-ion recombination reaction is used for the excitation of the quencher fluorescence 15°). Trans-stilbene is a chemically inert 162> triplet quencher which is especially efficient where the energy of the first excited triplet state of a primary product is about 0.2 eV above that of trans-stilbene 163>. This condition is realized, for example, in the energy-deficient chemiluminescent system 10-methyl-phenothiazian radical cation and fluoranthene radical anion 164>. 

At least experiments with fluoranthene and other aromatic hydrocarbons having lower triplet energies than fluoranthene resulted only in fluoranthene singlet emission- this excited singlet appears to be generated directly and not by triplet-triplet annihilation. 

Fig. 12. Perrin quenching radii, R, [33J vs. variations of the free energy, - AG°, of electron transfer from the excited donor molecule to the acceptor molecule for donor-acceptor pairs in vitreous /nms-l,5-decalindiol. 1, Rubrene + A/ AT-diethylamline (DEA) 2, rubrene + N,N,-Ar,Ar-tetramethyl-p-phenylenediamine (TMPD) 3, rubrene + tetrakis(dimethylaminoethy-lene) 4, tetracene + DEA 5, tetracene + TMPD 6, 9,10-dinaphthylanthracene + DEA 7, 9,10-dinaphthylanthracene + TMPD 8, perylene + DEA 9, perylene + TMPD 10, 9-methylanthracene + TMPD 11, 9,10-diphenylanthracene + TMPD 12, coronene + TMPD 13, benzo[ Ai jperylene + TMPD 14, fluoranthene + DEA 15, acridine + DEA.

Several different fluors have been tested for this application and the best results have been obtained for decacylene (Aex = 385nm Af = 510nm KSy = 0.62) embedded in silicone rubber film. Fluoranthene which has a higher value of fCsv requires UV excitation (Aex = 360 nm) and is therefore less convenient to use. 

Figure 2. Fluorescence spectrum in a nitrogen matrix at 15 K (excited by a 2.5-kW mercury-xenon lamp) of an adsorption chromatography fraction from a coking plant water sample. Compounds BbF, benzo[b]fluorene C, chrysene BeP, ben-zo[e]pyrene P, pyrene BkF, benzo[k]fluoranthene BaP, benzo[a]pyrene U, unknown ( ).

The analysis of PAHs by fluorescence detection HPLC is often the water analysts first introduction to HPLC. The analysis of the WHO six PAHs (section 11.8.1.1) namely fluoranthene, benzo[6]fluoranthene, henzo[k]fluoranthene, benzo[a]pyrene, benzo[g/j/ perylene and indeno[l,2,3-cd]pyrene was carried out using fixed excitation and emission E wavelengths. With the advent of relatively cheap variable wavelength programmable fluorescence detectors, the detectors can be optimised for each separate PAH with a resultant lowering of detection limit. Ultratrace determination of PAHs down to 180fg of benzo[a]pyrene was reported as early as 1983. 

Nickel, B., Delayed Fluorescence from Upper Excited Singlet States S (n > 1) of the Aromatic Hydrocarbons 1,2 Benzanthracene, Fluoranthene, Pyrene, and Chrysene in Methylcyclohexane, Helv. Chim. Acta 1978, 61, 198 222. 

Figure 6 Lamp-excited Ml spectra of chromatographic fraction of coking plant wastewater, in nitrogen (upper spectrum) and n-heptane (lower spectrum) matrices at 15K. BbF = benzo[P]fluor-orene, C=chrysene, P = pyrene, BkF = benzo[k]fluoranthene, BaP = benzo[a]pyrene, Pe = perylene, U = unidentified.

Polycyclic aromatic hydrocarbons (PAHs) are produced through the incomplete combustion of various materials. Air-suspended particulates adsorb PAHs so air and subsequently soil and sand will also be contantinated. PAHs generally exhibit strong carcinogenic and mutagenic activity. For example, benzo[a]pyrene (B[a]P) is known as a carcinogenic compound. Synchronously excited fluorescence spectrometry has provided a multicomponent analysis of PAHs (135). After ultrasonic extraction of PAHs, e.g., B[a]P benzo[k]fluoranthene (B[k]F), chrysene (Chry), benzo[a]anthracene (B[a]A), pyrene (Py), perylene (Pery), and benzo[ghi]petylene (B[ghi]pery), from soils, they were separated by TLC on kieselguhr G layers mixed with 26% acetylated cellulose (135). Twelve PAHs... 

For triplet states, excitation yield values up to unity were measured for the energy-deficient system fluoranthene/lO-methyl-phenothiazine [14,18]. The estimation of the triplet yield was carried out by interception with cis-stilbene (p. 57). 

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