Chromophore concept

Further analysis is based on the idea that the characteristic experimental behavior of different classes of compounds and the suitability of those or other models used to describe this behavior is ultimately related to the extent to which chromophores responsible for the observed behavior and physically present in the molecular system are reflected in these models by adequate electron groups. The TMCs of interest, can be physically characterized as those bearing the 4-shell chromophores. (The analogy between the chromophore concept and McWeeny s theory for the special case of TMCs has also been noticed early in a remarkable work [149]). The basic features in the electronic structure of TMCs of interest, distinguishing these compounds from others, are the following ... 

The later discovery of the iron(II) complexes of aliphatic a-diimi-nes (IV),e. g. glyoxalbismethylimine (GMI) and biacetylbismethylimine (BMI) (/7) and of 2-pyridinMimines (V) 12—16) with spectral characteristics very similar to those of the bipy and phen complexes, corroborated Sone s chromophore concept. Electron delocalization within... 

Sullivan, P.A., S. Bhattacharjee, B.E. Eichinger, K Firestone, B.H. Robinson, and L.R. Dalton. 2004. Exploration of series type multifuctionalized nonlinear optical chromophore concept. Proc SPIE 5351 253-259. 

A major trend in organic synthesis, however, is the move towards complex systems. It may happen that one needs to combine a steroid and a sugar molecule, a porphyrin and a carotenoid, a penicillin and a peptide. Also the specialists in a field have developed reactions and concepts that may, with or without modifications, be applied in other fields. If one needs to protect an amino group in a steroid, it is advisable not only to search the steroid literature but also to look into publications on peptide synthesis. In the synthesis of corrin chromophores with chiral centres, special knowledge of steroid, porphyrin, and alkaloid chemistry has been very helpful (R.B. Woodward, 1967 A. Eschenmoser, 1970). 

The concept of a chromophore is analogous to that of a group vibration, discussed in Section 6.2.1. Just as the wavenumber of a group vibration is treated as transferable from one molecule to another so is the wavenumber, or wavelength, at which an electronic transition occurs in a particular group. Such a group is called a chromophore since it results in a characteristic colour of the compound due to absorption of visible or, broadening the use of the word colour , ultraviolet radiation. 

Itishould be noticed that the similarity between the osmophore theory and Witt s chromophore colour theory does not extand much beyond the initial conception and there seems to be no connection between the odour and the colour of a body, it is indeed quite the exception for a body to have both a strong odour and a strong colour. Two prolific sources of colour, viz. the diazo group and a large molecule have no counterpart as regards odour, and it is probably only by chance that quinone and chroman both have pronounced odours and are the sources of colour. 

Figure 11. Schematic representation of the concept of a Figure 10 A, B, and C are suitably chosen chromophoric three-pole supramolecular switching of energy transfer. The groups. For more details, see the text, cartoons correspond to the molecular components shown in...

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