1- Methyl-naphthalene. fluorescence

Schwarz, F.P., Wasik, S.P. (1977) A fluorescence method for the measurement of the partition coefficients of naphthalene, 1-methyl-naphthalene, and 1-ethylnaphthalene in water. J. Chem. Eng. Data 22, 270-273. 

Kawakubo s fluorescence results 86> for methyl- and dimethylnaphthalene solids can be similarly related to the crystal structure. Both 2-and 2,6-substituted naphthalenes retain the same close-packed layer structure as seen in naphthalene. The only effect of the methyl substitution is to increase the crystal dimension along the naphthalene long axis87 . Less is known about the crystal structures of 1- and 1,6-substituted naphthalenes, except that the 1-substituent requires a different packing pattern than naphthalene and that 1- and 1,6-substituted naphthalenes have much lower melting points than the 2-substituted naphthalenes. The absence of sandwich pairs in 2- and 2,6-substituted naphthalene crystals certainly explains the lack of excimer fluorescence in the crystal spectra. Presumably, such pairs are also absent in crystalline 1-methylnaphthylene, but they seem to be present in glassy 1-methyl-naphthalene and in 1,6-dimethylnaphthalene solid. 

Naphthalene, 1-methyl-naphthalene, and acenaphthene fluorescence in water is quenched by trimethylamine (TMA) without the formation of an... 

One such method is sensitised fluorescence (see additional remarks on this subject in Chap. 6). Here, the detection limit for fluorescing compounds lies at less than 10" molecules/host molecule or ca. 10 impurity molecules per cm. Fig. 3.6 shows as an example of such a measurement the detection of -methyl-naphthalene in naphthalene. Still more sensitive is the method of sensitised delayed fluorescence (Sect. 6.9). Here, the detection limit is at ca. 10 molecules/host molecule or 10 impurity molecules per cm [5,6]. 

Fig. 3.6 In the fluorescence spectrum of naphthalene at 4.2 K, the impurity concentration of -methyl-naphthalene can be estimated from the intensity ratio of a vibronic naphthalene line and the 0.0 line of )3-methyl-naphthalene to be 3 10 . After [3].

Two major impurities [l,3-dimethyl-2-phenylnaphthalene, l-benzyl-3-methyl-naphthalene). found in illicit synthetic metamphetamine were separated on a Cjg column (2 = 228 ran) using a 70/30 acetonitrile/water mobile phase [1420]. Elution was complete in 4 min and peaks were baseline resolved. Fluorescence detection (A = 228 ran, ex 340 nm, em) was approximately 30 times more sensitive (165pg/mL vs. 3.9ng/mL, with S/N = 3 for both). For fluorescence work the total elution time was 12 min. 

N-methyl acridone fluorescence. Similarly, naphthalene-2,3-dicarboxylic acid hydrazide has a very low chemiluminescence efficiency (about 5 x 1(T ), and a mixture of this hydrazide with DP A (both KT M) yields no more light than does the hydrazide alone. 

The same authors studied the CL of 4,4,-[oxalylbis(trifluoromethylsulfo-nyl)imino]to[4-methylmorphilinium trifluoromethane sulfonate] (METQ) with hydrogen peroxide and a fluorophor in the presence of a, p, y, and heptakis 2,6-di-O-methyl P-cyclodextrin [66], The fluorophors studied were rhodamine B (RH B), 8-aniline-l-naphthalene sulfonic acid (ANS), potassium 2-p-toluidinylnaph-thalene-6-sulfonate (TNS), and fluorescein. It was found that TNS, ANS, and fluorescein show CL intensity enhancement in all cyclodextrins, while the CL of rhodamine B is enhanced in a- and y-cyclodextrin and reduced in P-cyclodextrin medium. The enhancement factors were found in the range of 1.4 for rhodamine B in a-cyclodextrin and 300 for TNS in heptakis 2,6-di-O-methyl P-cyclodextrin. The authors conclude that this enhancement could be attributed to increases in reaction rate, excitation efficiency, and fluorescence efficiency of the emitting species. Inclusion of a reaction intermediate and fluorophore in the cyclodextrin cavity is proposed as one possible mechanism for the observed enhancement. 

Free formaldehyde is reacted with acetylacetone in the presence of an excess of an ammonium salt to form the yellow fluorescent compound, 3,5-diacetyl-1,4-dihydrolutidine and subsequently determined spectrophotometrically in methods A-E (14). In these methods, the test sample must be colorless and free from other carbonyl compounds. Some other derivatives have been used to analyze formaldehyde. For example, formaldehyde was reacted with sodium 4,5-dihydroxy-2,7-naphthalene disulfonate in sulfuric acid solution to yield a purple color (580 nm) and then subjected to colorimetric analysis. A purple-colored pararosaniline derivative was used to analyze formaldehyde in air (15). Air sample was passed through an aqueous solution which contained 0.4% of 3-methyl-2-benzothiazolone hydrazone hydrochloride and then a dye produced was determined at 635 or 670 nm (16). Molecular sieve (1.6 mm pettet) was used to trap formaldehyde in air samples. The formaldehyde... 

Di-(l-naphthylmethyl)sulphone forms an excimer but does not react to give an intramolecular cycloaddition product like the corresponding ether but rather fragments to give sulphur dioxide and (l-naphthyl)methyl radicals (Amiri and Mellor, 1978). I-Naphthylacetyl chloride has a very low quantum yield of fluorescence and this is possibly due to exciplex formation between the acyl group and the naphthalene nucleus (Tamaki, 1979). Irradiation leads to decarbonylation. It is known that acyl chlorides quench the fluorescence of aromatic hydrocarbons and that this process leads to acylation of the aromatic hydrocarbon (Tamaki, 1978a). The decarboxylation of anhydrides of phenylacetic acids [171] has been interpreted as shown in (53), involving... 

The series of copolymers of 1-vinyl naphthalene with methyl methacrylate used in a recent study is shown in Table 3 ete the fonctions are the mole fraction of naphthalene chromophores in the copolymer, fn the fraction of linkages between naphthalene species in the polymer chain, f n, and the mean sequence length of aromatic species, 1 . Fluorescence decays in the monomer and excimer emission... 

To illustrate the capabilities of the system shown in Fig. 16.12, we present new, previously unpublished results from our laboratory. In Fig. 16.13, we illustrate results for three fluorescent probe molecules (pyrene, DCM [4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran], and PRODAN [6-propionyl-2-(/V,/V-dimethylamino)naphthalene]) that were doped within a series of PFFA/Pluronic P104 BP blends. In the initial experiments, 16 BP formulations were prepared manually using micropipettes, while subsequent experiments utilized the ALHS to prepare 21 BP formulations. These formulations were spun cast into thin films employing quartz microscope slides as substrates. To characterize the local microenvironment surrounding each probe within a given formulation, steady-state fluorescence measurements using a conventional spectrofluorometer were performed. 

The fluorescence of the phenyl polymer is similar in shape to the fluorescence from the alkyl polymers and the similar shape of the phosphorescence spectrum, as well, suggests that the origins of the electronic spectrum are also much the same. The apparent increased quantum yield for phosphorescence in poly(phenyl methyl silylene) probably reflects a mixing of the ring electronic levels with the levels of the chain. Both the fluorescence and phosphorescence of the naphthyl derivative are substantially altered relative to the phenyl polymer. Fluorescence resembles that of poly(B Vinyl naphthalene) (17,29) which is attributed to excimer emission. Phosphorescence is similar to naphthalene itself. These observations suggest that the replacement of an alkyl with phenyl moiety does not change the basic nature of the electronic state but may incorporate some ir character. Upon a naphthyl substitution both the fluorescence and phosphorescence become primarily tt-tt like. 

Figure 7. Two-color fluorescence spectra of the I-naphthylmethyi and 2-naphthyl-methyl radicals. Spectra were produced by excitation of the sample with a 25-ps, 266-nm laser pulse followed by a 25-ps, 355-nm pulse delayed by 60 ps. Key to (halo-methyljnaphthalenes a, I-(chIoromethyI)naphthaIene b, 2-(chloromethyl)naphthalene c, I-(bromomethyI)naphthalene and d, 2-(bromomethyl)naphthalene. Note the fluorescence in the blue region of Spectrum c is due to impurities that contaminated the sample of l-(bromomethyl)naphthalene (28).

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