Hypsochromic spectral shifts

On the basis of the UV spectra of the neutral forms of cytosine and of the bathochromic and hypsochromic spectral shifts caused by protonation of cytosine and of its 1-methyl, 3-methyl, 5- and 6-halogeno derivatives, Wempen and Fox105 have concluded that 6-chloro and 6-fluorocytosine were best represented by the form 3 in which the dissociable proton was affixed to N-3. 5 - Ha I ogenocytosines by contrast occur mainly as form 2. 

Figure 11.24 shows the change of fluorescence intensity (normalized to the pure ACRAM spectrum) with the addition of photoresist solution formulated from poly(CBN-a/ -MAH) and TPSHFA (4.41 x 10 M). These spectra show hypsochromic spectral shifts of the peaks around Xi 440 430 nm and X2 470 460 nm, as well as an increase in the intensity of these peaks, indicating the protonation of ACRAM/THF solution by the photogenerated acid. " ... 

Fig.14A, B. Potential energy curves of adsorbed molecules in the ground (lower curve) and the excited state (upper curve) for the explanation of bathochromic (A) and hypsochromic spectral shifts (B) according to de Boer. Reprinted from [18] with kind permission of R. Oldenbourg Verlag GmbH, Miinchen...

A new simple and reliable method for monitoring photoinduced acid generation in polymer films and in solutions of the kind used in 193 nm and deep-UV lithography was developed. By using N-(9-acridinyl)acetamide, a fluorescent acid-sensitive sensor, we have been able to study the effects of trifluoroacetic acid and photoacids generated from triphenylsulfonium hexafluoroantimonate on the spectral properties of the acid sensor in THF solution and in alicyclic polymer resist films exposed at 193 nm. In both cases a hypsochromic spectral shift and an increase in fluorescence intensity were observed upon protonation. This technique could find application in the study of diffiisional processes in thin polymer films. 

The x-band in malachite green arises from an NBMO—>n transition, so that 3- and 4-substituents affect the energy of the excited state only and bring about spectral shifts of the first absorption band which vary linearly with the appropriate Hammett substituent constants. Thus, electron-withdrawing groups cause bathochromic shifts of the x-band whereas donor substituents cause hypsochromic shifts (Table 6.6) [64,67]. The 3-band arises from a n—>n transition [68] so that substituent effects are less predictable. As the donor strength of the 4-substituent increases, however, the 3-band moves bathochromically and eventually coalesces with the x-band - at 589 nm in the case of crystal violet (6.164), which possesses two NBMOs that are necessarily degenerate [69]. 

Fig. 3 Typical ICT probes (left) and representative spectroscopic responses toward selected metal ions (right). Color code (left) coordinating atoms in blue, bridgehead atom of the fluorophore that takes part in complexation in orange, formal donor fragment in red, formal acceptor fragment in green (right) hypsochromic shifts in red, bathochromic shifts in green, fluorescence enhancement in violet, fluorescence quenching in blue. Symbols in table Aabs, 7em,

Moreover, bulk MIP was prepared [56] exhibiting diastereoselectivity for cinchona alkaloids. In the presence of MIP in solution, the cinchonidine fluorescence emission was hypsochromically shifted with the increase of the cinchonide concentration. That is, maximum of the fluorescence emission was at 390 nm in the absence of cinchonidine whereas it was at 360 nm at higher concentrations of cinchonidine. When cinchonidine was examined in the absence of MIP or in the presence of NIP, there was no spectral shift or this shift was negligibly small. This shift has been explained on the basis of protonation of the nitrogen atoms present in the cinchonidine structure. 

Kronman et al. (1965) and Kronman and Holmes (1965) appear to be the first to have studied the effects of acid on a-lactalbumin and report that this protein, adjusted to pH values below its isoelectric point, exhibits a hypsochromic shift in its absorption spectrum between 270 and 300 nm. Spectral shifts in this region usually reflect changes in the environment of Trp and Tyr residues. The conformational change is a complex one, involving a series of steps. Because of the nature of the shift, the numbers of Trp and Tyr residues present, and the relative magnitudes of e for Trp and Tyr, Kronman and co-workers concluded that the shift results from environmental alterations for more than one of the buried Trp residues. (At the time of this study, three Trp residues were considered to be buried in bovine a-lactalbumin.) There appears to be no corresponding effect for hen egg-white lysozyme. [However, note the effect of acetic acid studied by Kato et al. (1984).]... 

A shift in A,max to shorter wavelength is called a hypsochromic effect, or blue shift, and usually occurs when compounds with a basic auxochrome ionise and the lone pair is no longer able to interact with the electrons of the chromophore. Hypsochromic effects can also be seen when spectra are run in different solvents or at elevated temperatures. Spectral shifts of this type can be used to identify drugs that contain an aromatic amine functional group, e.g. the local anaesthetic benzocaine (see Figure 7.9). 

Figure 25.3 shows the UV-vis spectral change from 1 to 2 in a microcrystalline powder film. The hypsochromic (blue) shift of A,m lx from 510 to 475 nm was... 

Spectral shift can be bathochromic or hypsochromic depending on the nature of molecular design. An electron donating group (that belongs to both receptor and... 

In a related phenomenon, the spectral shifts which accompany aggregation-deaggregation have been reported as a basis of yet another erasable medium.24 The active layer consists of discrete particles of a cocrystalline complex of a pyrylium dye with a polymer such as polycarbonate. Pulsed irradiation of this aggregated film resulted in an instantaneous deaggregation process which was accompanied by a hypsochromic shift of about 100 nm. The recording mechanism is believed to be thermal and a thermal erasure (reaggregation of the dye-polymer complex) was also demonstrated. 

In the UV spectral range complexation with 18-crown-6 causes a hypsochromic shift of the band with the longest wavelength in various solvents (Bartsch et al., 1976 Hashida and Matsui 1980). Gokel and Cram (1973) reported that complexation with binaphtho-20-crown-6 (11.2) produces a yellow to red color. This phenomenon is very likely to be due to a charge-transfer band between a naphthalene ring as donor (7i-base) and the arenediazonium ion as acceptor (7i-acid). 

Geometrical cis-trans isomers — The UV-Vis spectra of most cis isomers are similar to those of the corresponding dll-trans isomer. However, a few consistent differences can be found in the spectra of cis isomers as compared to those from the corresponding a -trans compound a hypsochromic shift (2 to 6 nm for mono-dY through 34 nm for tetra-c ), a decrease in absorbance, a reduction of the spectral fine structure, and tlie appearance of a new absorption band known as a cis peak. For example, in a study in which the structures were confirmed by NMR, the isomers... 

The alteration of hemoprotein(s) P-450 subpopulations in the rat may be observed spectrally, because after treatment of rats with polycyclic aromatic hydrocarbons, the Soret maximum of the carbonmonoxyferrocytochrome complex undergoes a hypsochromic shift from 450 to 448nm (50). This blue shift was not seen with rainbow trout hepatic microsomes (29,30). However, this does not preclude the induction of novel hemoproteins P-450 since (a) the induced hemoprotein(s) maty not differ spectrally from the constitutive enzymes and (b) the induced-hemoprotein may account for only a small proportion of total hemoprotein P-450, and hence its contribution to the position of the Soret maximum of carbon monoxide-treated reduced microsomes may be negligible. The latter suggestion is supported by the work of Bend et al. with the little skate. These workers have shown that hepatic microsomes from 1, 2,3,4-dibenzanthracene treated skates did not exhibit a hypsochromic shift when compared to control microsomes, however, partially purified hemoprotein exhibited an absorbance maxima at 448 nm (51). 

Two differential spectrophotometric methods were used by Chatterjee et al. for the simultaneous analysis of diloxanide furoate and metronidazole in pharmaceutical formulations [24]. The first method involved measurement of the absorbance of a methanolic solution of the two drugs at 259 and 311 nm. Since the absorbance of diloxanide furoate at 311 nm is zero, the concentration of metronidazole is directly measured, and a simple equation based on absorbance ratios is used to calculate the concentration of diloxanide furoate. The second method was a differential spectrophotometric determination based on pH-induced spectral changes, on changing from an acidic to an alkaline solution. A marked bathochromic shift was exhibited by metronidazole, while diloxanide furoate showed a slight hypsochromic shift. The wavelength of maximum absorption difference for diloxanide furoate was 267 nm, where metronidazole did not absorb. Similarly, diloxanide furoate did not interfere with metronidazole at when measured at 322 nm. 

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