Chromophore/chromogenic group

The nature and position of some substituents (auxochromes), i.e. —OH, —OR,—NHj, etc. groups) which extend the conjugation of a chromophore by sharing of the nonbonding electrons and thus become a new extended chromophore (chromogene). 

Chromophore - the unsaturated building blocks of colour, i.e. -N=N-, carbonyl and nitro groups etc. (see also chromogen). 

Chromophores (or oxochromes) are small groups of atoms responsible for characteristic absorptions. By extension, the chromophore in a molecule corresponds to the site responsible for the electronic transition. A chromogene is a species formed by a skeleton on which many chromophores can be found. For a series of molecules containing the same chromophore, the position and intensity of the absorption bands are constant (Table 11.1). When a molecule contains several isolated chromophores separated by at least two single bonds, the overlapping of individual effects is observed. If the chromophores are adjacent to one another, a different situation results. 

These hosts include simple anion sensor systems containing urea, thiourea, amine, amide, alcohol, and pyrrole groups linked to chromophores. Chro-mophores used in this type of chromogenic anion sensors are mainly organic dyes such as azobenzene, nitrobenzene, indoaniline, and anthraquinone or... 

The quinones belong to the most powerful class of chromogens, and this is equally true of both the para- and orthoquinones. They yield actual dyestuffs by introduction of auxochromic groups. The oxyquinones possess a specially marked dyestuff-character, as the quinone group belongs to the acid-forming chromophors, and the hydroxyl group introduced develops powerful acid properties. 

The amount of nonbound analyte can be quantified directly, especially if it contains a strong chromophore, fluorophore, or isotope label. Alternatively, it can be postlabeled or the evaluation can take place in a competitive or displacement assay format using a labeled probe.3132 A final option is to incorporate a signaling group in the imprinted site leading to a chromogenic response reflecting the amount of bound analyte.3334... 

The functional groups of organic compounds (ketones, amines, nitrogen derivatives, etc.), responsible for absorption in UV/Vis are called chromophores (Table 9.1). A species formed from a carbon skeleton transparent in the near UV on which are attached one or several chromophores constitutes a chromogene. 

Figure 2.3 Ninhydrin Test. Ninhydrin combines with a-iV-primary amine functional groups to form primary amine product that combines with a second molecule of ninhydrin to generate a chromogenic chromophore.

O. N. Witt assumed that coloured compounds contain atomic groupings which he called chromophors. Compounds containing chromophors he called chromogens although coloured they are not dyestuffs and have no affinity to tissues. Nitrobenzene is coloured but is not a dye. To produce dyes, the presence of groups such as OH or NHg is also necessary, which Witt later called auxochromes, Witt named as chromophors only the groups NO2, — N=N—, and CO occurring twice in quinones. ... 

The molar absorptivity (s) is constant for a particular chromophoric group (or chromogen) at a given wavelength. Where values for e are very large, it is convenient to express it as its logarithm (logipE). The absorbance (extinction) is a cumulative property for a mixture of two or more components ... 

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