Bathochromic and hyperchromic shifts

Figure 24 shows the bathochromic and hyperchromic shifts of the of DNA on addition of increasing rj quantities of NjPjAzg to the medium. These effects... 

N3PjA2 and N P AZg, which exhibit significant activity against either L1210 and P388 leukemias or B16 melanoma, induce a noticeable fluorescence decrease and bathochromic and hyperchromic shifts ... 

The chromophore of phenylephrine is not extended but its structure includes a phenolic hydroxyl group. The phenolic group functions as an auxochrome under both acidic and alkaline conditions. Under acidic conditions it has two lone pairs of electrons, which can interact with the benzene ring and under basic conditions it has three. Figure 4.11 shows the bathochromic and hyperchromic shift in the spectrum of phenylephrine, which occurs when 0.1 M NaOH is used as a solvent instead of 0.1 M HCl. Under acidic conditions the X max is at 273 and has an A (1 %, 1 cm) value of 110 and under alkaline conditions the X max is a 292 nm and has an A (1%, 1 cm) value of 182. 

It is well known that anthocyanins with hydroxyl groups in orr/zo-position to each other form complexes with aluminum ion leading to bathochromic and hyperchromic shifts in their absorption spectra. Complexation of AF" " with synthetic and natural anthocyanins has been investigated in aqueous solutions within the pH range 2 to 5. As shown by UV-vis... 

Mercaptans (R-SH) [35] are weak acids (pKa around 10) and give rise to an equilibrium in aqueous solution. In basic media, bathochromic and hyperchromic shifts are observed in all cases. This effect is particularly marked with thiophenate ion because of a stabilisation of the negative charge with the n electrons of the aromatic ring. By adjusting the pH of sample to 11 after addition of sodium hydroxide solution 2.5 M, the spectra show a well-defined peak of absorbance at 238 nm for the alkylthiols or 263 nm for the thio-phenols. The application of the deconvolution method allows the estimation of the global concentration of mercaptans in wastewater. 

The bathochromic and hyperchromic shifts of n—mi or ti—mi absorbances (Figure 17.5) of the aryl rings caused by the introduction of two alkoxy groups correlated well with the increased photolability of nitroveratryl linkers during 365 nm irradiation. 

Figure 17.5 Bathochromic and hyperchromic shifts of n-Mt orTt-Mt absorbances of nitrobenzyl-derived photolabile linkers 13 (—) 14 ( ) 15 (- ), and phenacyl (—).

Substitution on the benzene ring can cause bathochromic and hyperchromic shifts. Unfortunately, these shifts are difficult to predict. Consequently, it is impossible to formulate empirical rules to predict the spectra of aromatic substances as was done for dienes, enones, and the other classes of compounds discussed earlier in this chapter. You may gain a qualitative understanding of the effects of substitution by classifying substituents into groups. 

The strain energies in the twisted polyarenes have been determined by comparison of heats of combustion with those of the corresponding nonstrained isomers. In the case of 4,5-dimethylphenanthrene, the comparison was with that of 2,7-dimethylphenanthrene [15]. The bathochromic and hyperchromic shifts of the UV spectra of twisted arenes have been used to detect the presence of twisted distortion [16]. 

However, the spectrum of the dye solution containing 1% Peregal 0 is apt to be quite different from that of the dye in distilled water. Pronounced bathochromic and hyperchromic shifts frequently occur (see Fig. 5). 

Bromothymol blue (pH range 6.2-7.6) is a triphenylmethane derivative, the chemical structure and spectral behaviour of which are close to the ones of phenol red (Fig. 23). In basic medium, a strong bathochromic and hyperchromic effect can be noted (7 = 615 nm, e = 17800 Lmol-1 cm-1). The colour turns from yellow (X = 433 nm, e = 5900 Lmol-1 cm-1, pH = 5.0) to blue (pH = 12.0). The bromine atom located on the phenolic ring induces a more intense bathochromic shift than for Phenol red. 

The marked changes in the carbonyl IR bands accompanying the solvent variation from tetrahydrofuran to MeCN coincide with the pronounced differences in colour of the solutions. For example, the charge-transfer salt Q+ Co(CO)F is coloured intensely violet in tetrahydrofuran but imperceptibly orange in MeCN at the same concentration. The quantitative effects of such a solvatochromism are indicated by (a) the shifts in the absorption maxima and (b) the diminution in the absorbances at ACT. The concomitant bathochromic shift and hyperchromic increase in the charge-transfer bands follow the sizeable decrease in solvent polarity from acetonitrile to tetrahydrofuran as evaluated by the dielectric constants D = 37.5 and 7.6, respectively (Reichardt, 1988). The same but even more pronounced trend is apparent in passing from butyronitrile, dichloromethane to diethyl ether with D = 26, 9.1 and 4.3, respectively. The marked variation in ACT with solvent polarity parallels the behaviour of the carbonyl IR bands vide supra), and the solvatochromism is thus readily ascribed to the same displacement of the CIP equilibrium (13) and its associated charge-transfer band. As such, the reversible equilibrium between CIP and SSIP is described by (14), where the dissociation constant Kcip applies to a... 

The optimum pH for formation of a ternary compound Fe(III)-ECR-CTA, suitable for Fe determinations, is 4.5 0.5. Maximal and stable absorbances (at 610 nm) are obtained when suitable (sufficiently large) concentrations of chromogenic reagent and cationic surfactant (see Procedure) are present in the sample solutions. In the ternary system a large bathochromic shift and hyperchromic effect are observed in comparison with the binary system (without CTA). 

Some PAH molecules include in their structure a five-membered cycle. When an aromatic ring is added to the linear chain containing the five-membered cycle, a bathochromic shift and hyperchromic effect are observed. 

As shown in Figure 7, n n - and n - 7t -transitions often behave differently. If cyclohexane (b) is replaced by methanol (a) as the solvent, the polarity increases considerably, so that the 71 - It band is shifted by 10-20 nm towards the red (bathochromic) and the n -> 7u -band by 10 nm towards the blue (hypsochromic). This shift gives an indication of the effect not only of the solvent polarity on the behavior of the bands, but also of the structure of the system. A change in intensity of the absorption band is described as hyperchromic (intensity increase) or hypochromic (intensity decrease) [5], [31]. 

Increasing the number of conjugated double bonds leads to a marked bathochromic shift and to a hyperchromic effect, as predicted by Woodward s and Fieser s rules8. 

Chenabine (99), C37H40N207, along with its 7 -0-demethyl analog, jhelu-mine (100, Section II,C,49), was isolated from Berberis lycium Royle (Ber-beridaceae). Chenabine shows [ajjy5 +40° (c 0.18, MeOH), IR 1680 cm 1 (aromatic aldehyde), NMR (CDC13) 8 3.25 (7 -OMe), 5.23 (s, H-8), MS m/e 624 (M+, 0.2%), 397 (base), and 227 (4, both from cleavage at a). The UV spectrum shows a bathochromic shift as well as a hyperchromic effect with base, typical of a p-hydroxybenzaldehyde. 

Thalictrum minus L. var. microphyllum (Ranunculaceae) was the source of the amorphous base (+)-uskudaramine (358), C39H44N208, [a] 5 +84° (c 0.15, MeOH). The structure proof of uskudaramine was simplified by comparison of its properties with those of the isomeric (+)-istanbulamine (173, Section II,C,47), isolated from the same source. Notably, the NMR spectrum of 358 lacks the H-8 (8 6.84) singlet of 173, and its UV spectrum shows not only a bathochromic base shift but also a hyperchromic effect, characteristic of a 3- or 9-hydroxyaporphine. 

Chemistry of multilayered cyclophanes has been reviewed and their physical and chemical properties have also been extensively discussed [52]. The UV spectra are known to show large bathochromic shifts with sizeable hyperchromic effects and become structureless as the number of layers increases. These features are more apparent for up to four-layered cyclophanes. This was explained primarily by the transannular n-n interaction/delocalization, while the effect of deformation of the benzene rings was thought to be rather negligible [53]. Despite the UV spectral study, only a limited amount of effort has been devoted so far to the study of the chiroptical properties of layered cyclophanes. 

Auxochrome An atom or group which, when added to or introduced into a chro-mophore, causes a bathochromic shift and/or a hyperchromic effect in a given band of the chromophore, usually in that of lowest frequency. This term is obsolete. 

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