Hypsochromic shift 1 effect

The hypsochromic shift effect on n electrons is much larger than the tt batho-chromic shift due to lowering of the tt orbital described above. As a consequence, the absorption maximum for the tt transition in a molecule which contains a lone pair of electrons... 

The shade may be varied by choosing amines. For aromatic amines, the steric effect of substituents in the ortho position reduces the conjugation of the anibno group with the anthraquinone moiety, and the result is a hypsochromic shift and brighter shade. Thus Cl Acid Blue 129 (120) has a more reddish and brighter shade than Cl Acid Blue 25 (118). Cycloalkylamines have a similat effect on the shade. Cl Acid Blue 62 [5617-28-7] (125) Cl 62045) is an example. 

Their physical properties closely resemble those of pterin, which has a basic pKt, of 2.20 and an acidic one of 7.86 associated with N-1 protonation and a hypsochromic shift of the long-wavelength absorption band in the UV spectrum, and N-3 deprotonation effecting a bathochromic shift respectively (Table 4). The xanthopterin (4) and isoxanthopterin types... 

The of 33 shows a bathochromic shift, compared to that of the corresponding spironaphthopyran [ max 531, 558(s) nm in toluene].78 The substituent effect in 2, 5, 6 - and 5-position of 33 on the absorption band of the colored form has been examined.72,77,7s The donor substituent group in 6 -position, such as piperidino group, gives a hypsochromic shift by 35 nm, but 5 -carbomethoxy substitution results in a bathochromic shift by 20 nm. This may be due to interaction between oxygen atom of the phenolate and methoxy group. 

Extension of -conjugation from naphthalene to anthracene and phenanthrene has a small effect on the tmax of the photomerocyanine form. Replacement of the indoline ring with piperidine, benzoxazole, or benzo-thiazole83 has resulted in hypsochromic shift by ca. 10 nm.72... 

Substituent effects on the are remarkable. Electron-withdrawing groups at the 5 -position, e.g., 5 -nitro-substitution (indoline component), and donor substituent at the 8-position (benzothiopyran component) in 44 leads to a longer wavelength shift. As the polarity of the solvent increases, the max of the colored form of spiroindolinobenzothiopyran results in hypsochromic shift. This can be interpreted as the existence of a polar structural component of the colored form in the ground state. Kinetic study has suggested that the zwitterionic structure largely contributes to the colored form of 6-nitrospiroindolinobenzothiopyran, as well as spiropy-rans.97 Based on H-NMR and X-ray analysis,98 99 the existence of an... 

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]. 

Shifts in absorption spectra due to the effect of substitution or a change in environment (e.g. solvent) will be discussed in Chapter 3, together with the effects on emission spectra. Note that a shift to longer wavelengths is called a bathochromic shift (informally referred to as a red-shift). A shift to shorter wavelengths is called a hypsochromic shift (informally referred to as a blue-shift). An increase in the molar absorption coefficient is called the hyperchromic effect, whereas the opposite is the hypochromic effect. 

An obvious difference was also noted between control and induced skate hepaticdnicrosomal AHH activity in the presence of a-naphthoflavone (10 M). This compound, when added in vitro at this or higher concentrations, caused significant stimulation of AHH activity in control animals (about 3-fold) but inhibition (80%) was found in DBA-pretreated skates. Similar results were earlier reported for control and 3-methylcholanthrene-treated rats (23), where it appears that the response is due to differential effects of a-naphthoflavone on hepatic microsomal cytochrome P-450 (stimulated) and cytochrome P-448 (inhibited) (24). Our data suggests that there may be a novel form of cytochrome P-450 synthesized in skate liver in response to polycyclic hydrocarbon administration, even though there was no hypsochromic shift in the carbon monoxide difference spectrum of dithionite reduced hepatic microsomes from DBA-treated skates (relative to hepatic microsomes from control fish). 

To estimate how many dye molecules fit into the dendritic micelles, UV-titra-tion experiments have been employed. In comparison with the spectra of a pure pinacyanol chloride solution in water, the peaks of the absorption maxima of the dye in the presence of the dendrimer are shifted bathochromically due to solvatochromic effects, which indicates the incorporation of the dye within the branches of the dendrimer. At dye-to-dendrimer molar ratios higher than 4 1, in addition to the bathochromic shifts, hypsochromically shifted peaks start to appear, indicating that the dendrimer is not incorporating further dyes. We interpret this as an incorporation of up to four dyes within the branches of the dendrimer. This observation correlates with the calculated available space within the dendrimer, obtained from the molecular simulations. Further studies of the interactions of the dyes within the dendritic micelle are in progress. 

A shift (also known as a red shift ) in a substance s electronic absorption spectrum toward longer wavelengths, as a consequence of a substituent, solvent, environment, or other effect. The opposite of a bathochromic shift is referred to as a hypsochromic shift. 

An effect observed in the spectrum of a chemical species in which a substituent, solvent, change in environment, or other effect causes the electronic absorption spectrum to shift to shorter wavelengths. The opposite effect is referred to as a bathochromic shift. The hypsochromic shift is also known as the blue shift. 

Introduction of dialkylamino substituents in the 6 -position of the spiroindolinonaphthoxazine (1.11) causes a hypsochromic shift in the absorption maximum of the coloured state and also an increase in its intensity. This hypsochromic shift can also be increased by introducing electron-withdrawing groups into the 5-position of (1.11), whilst electron-donating groups move the absorption maximum in the opposite direction. The data for these effects are given in Table 1.3. 

Pyrazoles with nonconjugating substituents show only one region of UV absorption (200-230 nm, log e= 3.1-3.8).14,15,30 Salt formation results in a bathochromic shift in and a small increase in log .8,47 With aryl conjugation there is a large bathochromic shift, and a second band appears.10,15,42,43,45,47 The illustrated examples 57-59,15 60,45 61, 62,47 and 13,8 show the effect of substituents and salt formation. A change of solvent from ethanol to hexane causes a small hypsochromic shift.45,47... 

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