Site photoactive chromophore

In contrast, if photoactive chromophores are covalently tethered to the polyelectrolyte main chain, the chromophore reactivity in the photoinduced ET is much more greatly changed because the reaction sites are totally constrained to the polyelectrolyte molecular surface. 

Nanoscale Morphological Change of PS-b-P4VP Block Copolymer Films Induced by Site-Selective Doping of a Photoactive Chromophore... 

Borgstahl, G. E., D. R. Williams, et al. (1995). 1.4A structure of photoactive yellow protein, a cytosolic photoreceptor unusual fold, active site, and chromophore. Biochemistry 34(19) 6278-6287. 

Therefore, it seems likely that the photoactive center is the chromophore CO group of particular species adsorbed and probably the monodentate acetate. These groups can be free or engaged with hydrogen bonds over acid Brdnsted sites. For the first, both the n-pp and TtSP transitions are red shifted, for the second the n-Jt is blue shifted while the Jt-Jt transition is red shifted. 

The speed of AgO formation is so rapid that it cannot be resolved by ns-laser photolysis techniques. Obviously, this effect has to be attributed to the close proximity of photoactive donor and Ag" " sites on the surface of the micelle. The photoinduced reduction of Ag" can be performed with a number of other donor chromophores such as porphyrins. 

In addition to the above mentioned basic requirements, there are a number of secondary factors upon which the success of a particular photoinitiated polymerization may depend. For example, the photoinitiator must possess absorption bands which overlap as nearly as possible the emission bands of the light source employed. It is important, therefore, to consider the emission spectra of various available light sources prior to undertaking the synthesis of a photoinitiator. Judicious placement of chromophors must be made. The introduction of a chromophor at positions remote to the site of the photolysis may not always result in the production of the desired photoactive bands due to inefficient transfer of energy within the molecule. One must consider the absorption characteristics of the photoproducts which result from irradiation of the photoinitiator. In some cases, the absorption of these compounds may overlap that of the photoinitiator and reduce its efficiency. Similarly, the monomers employed in the polymerizations should be as transparent as possible in the region of the spectrum absorbed by the photoinitiator. As a matter of practicality, one must also consider the solubihty of the photoinitiator in any given monomer system and even perhaps incorporate groups into its structure which enhance its... 

M. Hoff, W. D. Utmo, M. Active site stmcture of photoactive yellow protein with a locked chromophore analogue revealed by near-infrared Raman optical activity. J. Phys. Ghent Lett. 2013,4, 3031-3038. 

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