Fluorescent materials chromophores

In an extension of the Guerbet reaction, Obora and co-workers reported the development of an Ir-catalyzed reaction for the conversion of arylalkanols to a,(a-diarylalkanes [187], which have been widely used as chromophores and functional fluorescent materials [188-191]. 

Another advantage to examine these polyaers is that characterizations of ablated materials can be Bade possible by fluorescence spectroscopy. Fluorescence is very sensitive, and such surrounding aicroenvironaental conditions around the it -chromophore as polarity and viscosity and chroaophore aggregation can be probed. 

Time-resolved fluorescence has been used for the study of the PFR on poly(methyl methacrylate). It has been found that the photoproducts of 2-naphthyl acetate in some zones of the material act as long-range quenchers for the unreacted esters in other zones of the polymer. A nonrandom chromophore distribution is generated in this way [293]. 

Absolute measurements of the 2PA cross section of chromophores are experimentally very demanding and difficult to implement for routine studies of new materials. This is mainly due to the fact that the 2PA excitation rate in a sample does not depend simply on the square of the average intensity, (f(r, t)), but on the average of the square of the intensity, (f(r, t) ) (r and t are the special and temporal coordinate) [63,64,78]. These two quantities are not the same if the laser piflse has substructure in space and time [85,86]. Thus, absolute 2PA determinations that rely on the measurements of signals proportional to the excitation rate, such as the 2P-induced fluorescence... 

Since only polymers obtained from the cyclic starting materials 5, 6, 7, 10, 11 and 12, which are likely to have siloxene-like structures, exhibit color and fluorescence, the polysilane ring seems to be essential for the exceptional optical properties of siloxene. This is in agreement with the original idea of Kautsky, who assumed the cycle to be the chromophore. 

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