1- naphthol fluorescence

The crucial requirement of excited-state proton transfer (ESPT) is suggested by the failure of 1-naphthyl methyl ether to undergo self-nitrosation under similar photolysis conditions. The ESPT is further established by quenching of the photonitrosation as well as 1-naphthol fluorescence by general bases, such as water and triethylamine, with comparable quenching rate constants and quantum yield. ESPT shows the significance in relation to the requirement of acid in photolysis of nitrosamines and acid association is a photolabile species. 

The last case concerns the solvent molecules with large dielectric constants or strong basicity the ions can be rapidly solvated (in the bulk or in large clusters) and proton transfer occurs. Since the emission arises from the transferred state, the Stokes shift is important (typically around 9000 cm"1 with a large bandwidth). The 1-naphtholate fluorescence in neutral water or a mixture of polar solvents... 

In supercritical fluids, the possibility of local composition enhancements of cosolvent about a solute suggests that we should see enhancement of anion fluorescence if the water cosolvent clusters effectively about the 2-naphthol solute. Although in liquids the water concentration must be >30% to see anion emission, the higher diffusivity and density fluctuations in SCFs could allow stabilization of the anion at much lower water concentrations provided that the water molecules provide sufficient structure. Therefore the purpose of these experiments was to investigate 2-naphthol fluorescence in supercritical CO 2 with water cosolvent in the highly compressible region of the mixture to probe the local environment about the solute. 

Figure 7. 2-Naphthol fluorescence decay curves at pH = 3-43 (a) flash profile (b) 2-naphthol fluorescence intensity at 360 nm (c) 2-naphtholate fluorescence intensity at 450 nm (x 2-5 relative to (b)) (from Loken et al., 1972).

Figure 8. Acid dependence of 2-naphthol fluorescence (a) 2-naphthol (b) 2-naphtholate (Weller 1958a).

In a series of measurements devoted to the /J-naphtholate fluorescence quenchings, the results were also treated by the Marcus model and although the curves obtained were of the Rehm-Weller shape, the dGo value proposed by Weller did not fit the results [96], Again this value was found to be larger (5.8 Kcal) and the Marcus model more appropriate to understand the results (Fig. 2). 

Colorations with resorcinol and naphthol. Dissolve about 0-2 g. of resorcinol in I ml. of 30% aqueous NaOH solution, add i ml. of chloroform and warm gently the aqueous layer turns red and shows a slight fluorescence. 

Bromo-2-pyridyla2o)-5-diethylamiQophenol (5-Br-PADAP) is a very sensitive reagent for certain metals and methods for cobalt have been developed (23). Nitroso-naphthol is an effective precipitant for cobalt(III) and is used in its gravimetric determination (24,25). Atomic absorption spectroscopy (26,27), x-ray fluorescence, polarography, and atomic emission spectroscopy are specific and sensitive methods for trace level cobalt analysis (see... 

Purified by recrystn from xylene. Gives yellow-green fluorescent solutions at pH 8.2-9.5, [IR Schnopper et al. Anal Chem 31 1542 7959.] With AcCl naphthol AS-D acetate is obtained m 168-169°, and with... 

The reaction course has not been elucidated (cf. also sodium hydroxide reagent). Hydrolyzation reactions and aromatizations are probably primarily responsible for the formation of colored and fluorescent derivatives. Substituted nitrophenols - e.g. the thiophosphate insecticides — can probably be hydrolyzed to yellow-colored nitro-phenolate anions by sodium hydroxide or possibly react to yield yellow Meisenheimer complexes. Naphthol derivatives with a tendency to form radicals, e.g. 2-naphthyl benzoate, react with hydrolysis to yield violet-colored mesomerically stabilized 1,2-naph-thalenediol radicals. 

Premchandran RS, Banerjee S, Wu XK, John VT, McPherson GL, Ayyagari M, Kaplan D (1996) Enzymatic synthesis of fluorescent naphthol-based polymers. Macromolecules 29(20) 6452-6460... 

In addition, there is a large number of studies involving aromatic alcohols such as phenol [166] or naphthol, which have in part been reviewed before [21], These include time-resolved studies [21], proton transfer models [181], and intermolecular vibrations via dispersed fluorescence [182]. Such doubleresonance and more recently even triple-resonance studies [183] provide important frequency- and time-domain insights into the dynamics of aromatic alcohols, which are not yet possible for aliphatic alcohols. 

If pK is greater than 2, a plateau is observed for the relative fluorescence quantum yield of the acidic form and the basic form for pH ranging from pK to pK (Figure 4.10A) because of the absence of diffusional recombination. In fact, Eqs (4.59) and (4.60) which are relevant to this case show that /HA and IA- are constants. A typical example is 2-naphthol (pK = 9.3, pK = 2.8). 

The aqueous cores of reverse micelles are of particular interest because of their analogy with the water pockets in bioaggregates and the active sites of enzymes. Moreover, enzymes solubilized in reverse micelles can exhibit an enhanced catalytic efficiency. Figure B4.3.1 shows a reverse micelle of bis(2-ethylhexyl)sulfosuccinate (AOT) in heptane with three naphthalenic fluorescent probes whose excited-state pK values are much lower than the ground-state pK (see Table 4.4) 2-naphthol (NOH), sodium 2-naphthol sulfonate (NSOH), potassium 2-naphthol-6,8-disulfonate (NSOH). The spectra and the rate constants for deprotonation and back-recombination (determined by time-resolved experiments) provide information on the location of the probes and the corresponding ability of their microenvironment to accept a proton , (i) NDSOH is located around the center of the water pool, and at water contents w = [H20]/[A0T] >... 

The pK of tyrosine explains the absence of measurable excited-state proton transfer in water. The pK is the negative logarithm of the ratio of the deprotonation and the bimolecular reprotonation rates. Since reprotonation is diffusion-controlled, this rate will be the same for tyrosine and 2-naphthol. The difference of nearly two in their respective pK values means that the excited-state deprotonation rate of tyrosine is nearly two orders of magnitude slower than that of 2-naphthol.(26) This means that the rate of excited-state proton transfer by tyrosine to water is on the order of 105s 1. With a fluorescence lifetime near 3 ns for tyrosine, the combined rates for radiative and nonradiative processes approach 109s-1. Thus, the proton transfer reaction is too slow to compete effectively with the other deactivation pathways. 

W. R Laws and L. Brand, Analysis of two-state excited-state reactions. The fluorescence decay of 2-naphthol, J. Phys. Chem. 83, 795-802 (1979). 

Fig. 16.20 Fluorescence quenching (FQ) of 1-naphthol in the presence of HA as a function of pH and reaction time (1-naphthol = 8pmol LHA = 11 ppm C ionic strength of O.IM LiQ) F and F denote fluorescence intensities in the absence and in the presence of the quencher (HA), respectively. Reprinted with permission from Karthikeyan KG, Chorover J (2000) Effects of solution chemistry on the oxidative transformation of 1-naphtol and its complexation with humic acid. Environ Sci Technol 34 2939-2946. Copyright 2000 American Chemical Society...

Naphthol AS-D (3-hydroxy-2-naphthoic-o-toluide) [135-61-5] M 277.3, m 1196-198 . Purified by recrystn from xylene. Gives yellow-green fluorescent solutions at pH 8.2-9.5, [IR Schnopper et al. AC 31 1542 1959]. With AcCl naphthol AS-D acetate is obtained m 168-169 , and with chloroacetyl chloride naphthol AS-D-chloroacetate is obtained [Moloney et al. J His toe hem Cytochem 8 200 1960 Burstone Arch Pathology 63 164 1957],... 

Naphthol AS-acetate (3-acetoxynaphthoic acid anilide] [1163-67-3] M 305.3, m 152°, 160°. Recrystd from hot MeOH and dried in vacuo over P2O5. It is slightly soluble in AcOH, EtOH, CHCI3 or CgHg. It is a fluorogenic substrate for albumin esterase activity. [Chen and Scott Analyt Letters 17 857 1984], At kgx 320nm it had fluorescence at 500nm. [Brass and Sommer B 61 1000 1928]. 

Morra, M. J., Corapcioglu, M. O., von Wandruszka, R. M. A., Marshall, D. B. Topper, K. (1990). Fluorescence quenching and polarization studies of naphthalene and 1-naphthol interaction with humic acid. Soil Science Society of America Journal, 54, 1283—9. 

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