Hypsochromic shift solvent effect

The extinction coefficients of carotenoids have been listed completely bnt solvent effects can shift the absorption patterns. If a colorant molecnle is transferred into a more polar environment, then the absorption will be snbjected to a bathochro-mic (red) shift. If the colorant molecnle is transferred into a more apolar enviromnent, the absorption will be subjected to a hypsochromic (blue) shift. If a carotenoid molecule is transferred from a hexane or ethanol solution into a chloroform solution, the bathochromic shift will be 10 to 20 nm. 

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... 

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. 

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. 

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... 

It is shown that the characteristic absorption bands of the substances dissolved in supercritical carbon dioxide were subjected to show intense hypsochromic shifts compared with conventional organic solvents. In addition, bathochromic shifts of the absorption bands were effected by increasing C02 density. 

Hypsochromic shift the displacement of absorption to a shorter wavelength due to substituent or solvent effects. 

Tamura and Imoto [74] and Hendrickson, Drickamer et al. [182] observed pressure effects on the solution spectra of (44). In all solvents used they found a hyp-sochromic shift of the longest-wavelength absorption band with increasing pressure. The observed hypsochromic shift of a betaine solution in methanol amounts to Ad = — 15 nm (Av = +600 cm AEj = +1-7 kcal/mol) on raising the pressure from 1 to 10 kbar [182]. On the supposition that this piezo-solvatochromism results from better solute/ solvent interactions with increasing pressure, it can be stated that, the higher the pressure, the more polar the solvent, and the higher the t(30) value. 

Molecular EDA complexes as well as charge-transfer ion pairs show (negative) solvatochromism [128], i.e. the charge-transfer absorption maxima (2cx) undergo hypsochromic shifts with increasing solvent polarity. The solvatochromic effect is readily explained on the basis of the Marcus correlation for charge-transfer energies in solution [129], (Eq. 9) ... 

Merocyanine dyes and unsymmetrical cyanine dyes, however, have alternating bonds and exhibit in general a hypsochromic shift on steric hindrance 49 is an interesting dye that, depending on the solvent, shows for R = CH, either a bathochromic or a hypsochromic shift with respect to the parent compound with R = H. This effect will be explained in the following section. (Kiprianov and Mikhailenko, 1991.) ... 

Major evidence against the vibronic structure assignment comes from the specific solvent effects observed in alcoholic solvents. The Xmax of 2 is found to depart from the Xmax versus it relationship in Figure 2 in alcoholic solvents. Instead, Xmax shifts to shorter wavelengths as the steric hindrance around the hydroxy group increases, e.g. Xmax is 642.6 0.2 nm in primary alcohols, 639.4 nm in secondary alcohols and 634.1 nm in tertiary amyl alcohol. In conjunction with the hypsochromic shift, in intensity for the a-band The correlation between the... 

The ultraviolet (UV) absorption spectra of the heteroaromatic N-imines are dependent upon many factors, such as the nature of the parent heterocycles, substituents on the imino nitrogen, and solvent used. Usually pyridine N-acylimines show two intense absorption maxima at 230-235 and 330-360 nm in aprotic solvents such as dioxane, benzene, or chloroform, the latter band of which disappears by addition of acid.13,20,21,75,77 In protic solvents such as alcohol or water a hypsochromic shift and a hypochromic effect of the long-wavelength absorption are observed for example, pyridine N-benzoylimine shows a maximum at 352 nm (e 9700) in dioxane but at 313 nm (e 4650) in ethanol. 13,21 The long-wavelength absorption of pyridine N-ethoxycarbonylimine has been ascribed to a n-n transition on the basis of a Pariser-Parr-Pople (PPP) calculation and measurements of the absorption spectra of preoriented pyridine N-imines in polarized UV light.125... 

Although ultraviolet data on furoxans are widespread in the literature, going back to a very early paper of Milone,82 no systematic work has been performed. Dimethylfuroxan shows a broad band of medium intensity at 258 nm in ethanol,74,75,83 which is shifted to the red in aprotic solvents.75 A similar band is present in the spectra of other simple furoxans with chloro, acetyl, and dinitroethyl substituents,83 and also in bisdialkylaminofuro-xans,84 where the maximum is at somewhat longer wavelengths. Data are also available on isomeric cyclic acylfuroxans, e.g., 7,80 alkyl-aryl-furoxans,85 and amino-aryl-furoxans.86 In the last, hypsochromic and hypochromic effects are seen when the 3-phenyl isomer (8) carries an ortho substituent these are not observed in the isomeric 4-aryl derivatives (9).8 6... 

Polar compounds of a heterocyclic (6 5 6) system display a negative solvatochromism, the hypsochromic shift of the absorption maximum in solvents of increased polarity <80UKZ835, 92ZOB1903>. This effect is especially large for betaine (139) <85JOC4855>. 

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