Hypsochromic 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. 

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

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... 

It should be noted that the three solvent effects (polarity, acidity and basicity) contribute to increasing Et(30), i.e., to a hypsochromic shift in the transition of the probe (see Figure 10.3.6). 

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. 

Ultraviolet absorption spectra of thiophene derivatives were recorded using isooctane as a solvent (8). An apparent hypsochromic effect caused by the second nitro group in 2,5-dichloro-3,4-dinitro-thiophene was noticed. 

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... 

In some transitions, the polarity of the chromophore is weaker after absorption of radiation. One case of this is the n — jt absorption due to the carbonyl present in ketones in solution. Before absorption, the C+-0 polarisation stabilises in the presence of a polar solvent whose molecules will be clustered around the solute because of electrostatic effects. Thus, the n —> -rr electronic transition will require more energy and its maximum will be displaced towards a shorter wavelength, contrary to what would be observed in a nonpolar solvent. This is the hypsochromic effect. Because the excited state is readily formed, the solvent shell around the... 

Figure 11.7—Absorption spectrum ofbenzophenone in cyclohexane and ethanol. Note that the bathochromic and hypsochromic effects are reversed for the two types of transitions, depending on the nature of the solvent.

The effects of increased solvent polarity on the light absorption energy from the ground to the (Franck-Condon) excited state can be hypsochromic, if the ground state is more stabilized than the excited state or bathochromic if the opposite relative stabilization takes place. 

Fluorescence is affected by the medium, such as the solvent or surface. Polar media in general tend to enhance fluorescence and pH has a drastic effect creating hypsochromic or bathochromic shifts as well as... 

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. 

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