Absorption azides

Compound (159) has an IR band at 1070 cm-1, in neutral solution or the solid state, consistent with the tetrazole structure. In trifluoroacetic acid this band is replaced by a typical azide absorption at 2140 cm-1. Only in this solvent will photolysis give a good yield (91%) of the pyrimidinoindole (160) (72JOC3216). 

The heteroaromatic selenatriazole ring system (6) represents a new class of compounds isolated so far only as 5-amino-l,2,3,4-selenatriazoles. IR and mass spectra are in agreement with the selenatriazole structure and an alternative open-chain selenoacyl azide structure (7 X = Se) can be rejected because of the lack of an azide absorption in the IR heterocumulene region (ca. 2000-2300 cm-1) (82UP42800). 

Radiation-induced optical absorption bands have also been observed in nonalkali azides. Absorption spectra in Pb(N3)2 and TIN3 appear to be associated... 

The IR spectrum of Ca(N3)2-1.5N2H4 shows characteristic azide absorptions at 2080, 1310, and 640 cm while the absorptions at 3400, 3350,1655, 1600, 880, 820, and 600cm are due to hydrazine. The Zn-n frequency of N2H4 appearing at 880cm indicates the presence of hydrazine as an adduct. The absence of a j n-n frequency around 970 cm proves that N2H4 is not coordinated. The IR spectrum of Ba(N3)2 shows characteristic azide absorptions at 2080, 1310, and 640cm . ... 

Whereas currently most studies deal with azides, a similar effort devoted to other metal salts such as nitrates and chlorates would be an important step toward understanding electrical initiation of pyrotechnics, and conversely to making possible safe, non-expl igniters. For instance, a study by Maycock (Ref 4) shows that those azides, perchlorates, and nitrates in which the solid state shows absorption on the long wavelength side of the anionic excitation band in soln, are the most unstable members of the respective series. Consequently, there is a direct relationship between the absorption spectra of pyrotechnic oxidizers and their respective sensitivities... 

J.N. May cock et al, Electronic Absorption Spectra of Metallic Azides, Perchlorates, Nitrates and their Related Explosive Properties , SpectrochimicaActa 23A (1957), 2849—53... 

The formation of the acyl azide may be followed by the growth of the 2130-cm. (—N=N=N) infrared absorption of concentrated dichloromethane extracts of aliquots removed from the reaction. 

Puacz et al. (1995) developed a catalytic method, based on the iodine-azide reaction, for the determination of hydrogen sulfide in human whole blood. The method involves the generation of hydrogen sulfide in an evolution-absorption apparatus. In addition, the method allows for the determination of sulfide in blood without interference from other sulfur compounds in blood. A detection limit of 4 g/dm3 and a percent recovery of 98-102% were achieved. Although the accuracy and precision of the catalytic method are comparable to those of the ion-selective electrode method, the catalytic method is simpler, faster, and would be advantageous in serial analysis. 

Complex 6 exhibits an intense LMCT absorption band at 285 nm, which is shifted to longer wavelength and is more intense compared to the cis-isomer. Irradiation led to the disappearance of this band, indicating loss of azide. Photoactivation of the ira7zs-isomer initially resulted in the appearance of new Pt(IV) complexes (probably substitution of N3 for OH), as judged by 2D [1H, 15N] HSQC NMR, and after 60 min peaks for Pt(II) species appeared, including trans- [Pt(NH3)2(OH2)2]2+ (6r). 

Trace amounts of molybdenum were concentrated from acidified seawater on a strongly basic anion exchange resin (Bio-Rad AG1 X-8 in the chloride form) by treating the water with sodium azide. Molybdenum (VI) complexes with azide were stripped from the resin by elution with ammonium chlo-ride/ammonium hydroxide solution (2 M/2 M). Relative standard deviations of better than 8% at levels of 10 xg per litre were attained for seawater using graphite furnace atomic absorption spectrometry. 

Some characteristics of, and comparisons between, surface-enhanced Raman spectroscopy (SERS) and infrared reflection-absorption spectroscopy (IRRAS) for examining reactive as well as stable electrochemical adsorbates are illustrated by means of selected recent results from our laboratory. The differences in vibrational selection rules for surface Raman and infrared spectroscopy are discussed for the case of azide adsorbed on silver, and used to distinguish between "flat" and "end-on" surface orientations. Vibrational band intensity-coverage relationships are briefly considered for some other systems that are unlikely to involve coverage-induced reorientation. 

The UV spectra for the azide in a diethylene glycol dimethyl ether solution and for the styrene resin film with 1.0 micron thickness are shown in Figure 5. The azide has an intense absorption at around 248 nm (molar extinction coefficient at 248 nm = 3.0xl04 1/M cm). The syrene resin used as matrix polymer exhibits a significant transparency at 248 nm (70%). 

The UV spectra for this resist film, before and after exposure to KrF excimer laser irradiation for 100 mJ/cm2, are shown in Figure 6. The absorbance of the azide renders the reist film of l.o micron thickness essentially opaque at 248 nm. After exposure of 100 mJ/cm2, the absorbance bleaches from 0.5 to 6.0% at 248 nm. Intense absorption by this resist at 248 nm closely relates to the pattern profile of the resist, which will be discussed in the last section. 

As shown in Figure 6, the resist film strongly absorbs KrF excimer laser light. In the KrF excimer laser exposure of the resist, photon energy absorption is highest at the top of the resist film and lowest at the interface between the resist and substrate. This is due to the attenuation of the irradiation in the resist layer. Decreases in solubility followed by such photochemical reaction occur to a much greater extent in the vicinity of the resist film surface. Moreover, the thermally decomposed azide decreases solubility of the unexposed and exposed resist film (Figure 7). 

However, in the presence of NaN3, Br2 is rapidly transformed into a new species having an absorption maximum around 312 nm. This species is most likely BrN3, a material shown (75) originally by Hassner to be capable of ionic electrophilic addition to olefins. It has been demonstrated, (16) at least in neutral aqueous solutions, that BrN3 reacts with azide ions to give N2 and Br ... 

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