Porphins absorption spectra

The various porphyrinogens are colorless, whereas the various porphyrins are all colored. In the smdy of porphyrins or porphyrin derivatives, the characteristic absorption spectrum that each exhibits—in both the visible and the ultraviolet regions of the spectrum—is of great value. An example is the absorption curve for a solution of porphyrin in 5% hydrochloric acid (Figure 32-10). Note particularly the sharp absorption band near 400 nm. This is a distinguishing feamre of the porphin ring and is characteristic of all porphyrins regardless of the... 

Even if this porphine structure can be oxidised or reduced, it is usually considerably stable. It is characterised by an absorption spectrum having a specific band... 

Porphin, the parent substance, containing no side chains, is of the phyllo type (Fig. 3, curve). As side chains are added, the third band gradually increases in height as in 1,4-dipropionic acid porphin, is almost of the etio type in l,5-dimethyl-2,6-diethylporphin (124a) (Fig. 3, curve 2), and is of the etio type (or stepladder absorption spectrum) in the naturally occurring porphins (Fig. 4) in which all the pyrroles have side... 

In the fully substituted porphins, changing the relative positions of the side chains (with the exception of the C=0 groups) to form different isomers has no effect on the absorption spectrum. Substitution of one... 

Phthalocyaninato(2-)] iron(II) is a dark blue, thermally stable solid that can be sublimed in vacuo at 300°. It is very soluble in pyridine, giving deep blue solutions of the bis(pyridine) adducts. It also forms an unstable purple hexaaniline adduct when dissolved in aniline. It is soluble in concentrated sulfuric add and dimethyl sulfoxide (slightly) but is insoluble in most other organic solvents. The iron(II) complex, unlike the corresponding iron(II) porphines, is relatively stable toward oxidation to the iron (III) state. The electronic spectrum shows the following absorption bands (1-chloronaphthalene solution) 595 (e = 16,000), 630 (e = 17,000), 658 (e = 63,000) (pyridine solution) 333 (e = 45,000), 415 (e = 15,000), 395 (e = 2000), 658 nm (e = 8000). 

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. 

Metalloporphyrins possess highly characteristic absorption spectra, as exemplified by the spectrum of magnesium porphine. Fig. 5. There are two distinct regions of... 

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