Chromophore hyperchromic effect

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 This term is obsolete. 

The fluorescence of the other chromophore was efficiently but not totally quenched in the bifunctional systems but not at all in equimolar mixtures of the monofunctional models. All phosphorescence, however, occurred from the parabutyrophenone part, indicating very efficient triplet transfer. Bathochromlc shifts and a hyperchromic effect in the longest wavelength band of the absorption spectra are an indication for ground state interaction, which might lead to nonplanar conformations of the molecule playing a role in the excitation transfer. 

Irradiation of lower molecular weight samples in the fluid N phase at 313 or 366 nm led to an unusual result [21]. In the first few seconds of irradiation the perturbed spectrum of the N phase exhibited hyperchromism (an increase in absorbance) and its shape became similar to that of the spectrum of the isotropic melt. This effect is also observed upon triplet sensitization which, like 366-nm irradiation, suppresses photo-Fries rearrangement [28]. It has not yet been proved that this effect is accompanied by a phase change from N to I induced by photoproducts essentially acting as impurities in the mesophase. The effect could be at the microscopic level where formation of a cyclobutane dimer or other photoproduct could interrupt H-type aggregated chromophore stacks, or confor-... 

The Amux of absorption depends upon the microenvironment of the chromophore, as does the intensity of absorbance. For example, as just discussed, solvation can affect the energies of transitions. Binding of the chromophore to a receptor, natural or synthetic, can also often influence Amax/ as can a variety of other effects. When the shift in absorption is to shorter or longer wavelengths it is defined as a hypsochromic (blue shift) or bathochromic shift (red shift), respectively. When the intensity of absorption increases or decreases it is called a hyperchromic or hypochromic effect, respectively. 

---