Porphyrins Soret band

Another class of red dopants, tetraphenylporphyrins (63), offer a direct energy transfer from blue to red [151], The absorption bands comprise the sharp porphyrin Soret band at 418 nm and the weaker Q bands at 512 and 550 nm. The photoluminescence shows two sharp transitions at 653 and 714 nm and can be induced from a blue emitting host by Forster transfer to the Soret band and internal conversion to the Q bands. 

Figure 3. Transient absorption spectrum of a 2 x 10 M solution i in butyronitrile at 100 ps following a 0.3 mJ, 0.5 ps, 600 nm laser flash. Filters that reject stray excitation light cut out the 580-620 nm wavelength region, while the sharp cutoff at 440 nm is due to the intense absorption of the porphyrin Soret band at 419 nm.

We will show in this chapter that a designed combination of thermodynamic and/or kinetic control of the self-assembly processes has allowed us to develop various applications all based on the induced chirality in the porphyrin Soret band absorption region. Chiral information transfer has been followed using circular dichroism, a spectroscopic technique particularly useful to characterize (supra) molecular dissymmetry or chirality [3]. 

The absorption spectrum of 2 in dichloromethane is shown in Figure 3. It is similar to a superposition of the spectra of the carotenoid, porphyrin, and quinone components. The porphyrin Soret band at 420 nm dominates the spectrum. The porphyrin Q-bands in the 650, 590, and 550 nm regions are... 

Figure 10.30 shows the absorption and fluorescence spectra of 5,10,15,20-tetraphenyl-21H,23H-porphine (TPP).17 The chemical structure of TPP is inset. The porphyrin Soret band is seen as a strong, narrow absorption peak at 418 nm. The weaker absorption peaks at 512 and 550 nm are the Q bands, also typical of porphyrins. The fluorescence spectrum has peaks at 653 and 714 nm and the fluorescence quantum yield has been measured to be 11 % in solution exposed to air.66 The Soret absorption band has strong overlap with the fluorescence spectrum of PFO, resulting in efficient Forster transfer. The Forster-transfer radius has been calculated from the relative overlap of these spectra to be 4.8 nm. 

Figure 108. Diffuse reflectance spectra of zeolite Y with encapsulated Mn(TMP) showing porphyrin Soret band (top) and Mn(ll) ions (bottom). Reprinted with permission from Nakamura, M. iatsumi, T. Tominaga, H. Bull. Chem. Soc. jpn. 1990, 63, 3334.

Figure 18). The porphyrins were also metalated with Zn in order to produce stronger, substrate-induced changes in the porphyrin Soret band. However, in spite of expectations, there was no significant difference between the metalated and nonmetalated forms of the receptor. Binding affinities were analyzed by UV-vis titrations, and checked by... 

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