Chromophore length, effect

Barto, R.R., Jr., P.V. Bedworth, C.W. Frank, S. Ermer, and R.E. Taylor. 2005. Near-infrared optical-absorption behavior in high-beta nonlinear optical chromophore-polymer guest-host materials. II. Dye spacer length effects in an amorphous polycarbonate copolymer host. J Chem Phys 122 234907 1-14. 

The ability of carotenoids to be effective in photoprotection is dependent on chromophore length. This statement is based on in vivo and in vitro ob-... 

FIGURE 6.5 Effect of some structural changes of the chromophore on the ultraviolet (UV)-visible light absorption spectrum. (A) Increase of the chromophore length (B) CycUzation (C) Hydroxylation (D) Epoxydation. 

The magnesium porphyrin radical, Mg(tetraphenylporphyrin)C104 (136), has been used as a model for the structural and stereochemical consequences of loss of an electron in photosynthetic chromophores.521 The primary photosynthetic reaction in plants and bacteria consists of a transfer of an electron, in the picosecond time domain, from the chlorophyll phototrap to nearby acceptors yielding chlorophyll -cation radicals. The structure of (136) shows a five-coordinated Mg2+ cation which is not quite symmetrically sited in the porphyrin ring but has metal-ligand distances similar to those found in the previous structures. The perchlorate anion is tightly bound (Mg—O = 2.01 A) in a monodentate mode. It was concluded that the porphyrin can act as an electron sink and that no major effects are found in the bond lengths, or on the stereochemistry, of the macrocycle. 

Corrole contains an 1 S-7t-electron system and shows aromaticity similar to the porphyrin chromophore, with strong ring current effects on the peripheral and inner-proton NMR, relatively stable parent mass ion and intermediary C—C bond length between single and double bonds. 

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