Porphins fluorescence

Table 1. Common materials used in quenched-fluorescence oxygen sensing (Ru(dpp)3(C104)2 tris(diphenylphenantroline) ruthenium(II) perchlorate PtOEPK platinum(II)-octaethyl-porphine-ketone PtPFPP platinum(II)-tetrakis(pentafluorophenyl)porphine PS.poly(styrene), PSu poly(sulfone) PSB poly(styrene-butadiene) block co-polymer PVC polyvinylchloride) APET amorphous poly(ethyleneterephthalate) PE poly(ethylene).

Andrade SM, Costa SMB (2002) Aggregation kinetics of meso-tetrakis(4-sulfonatophenyl) porphine in the presence of proteins temperature and ionic strength effects. J Fluoresc 12 77-82... 

Baldo et al. [ 164] used the platinum complex of 2,3,7,8,12,13,17,18-octaethyl-21 //,23//-porphine (PtOEP, 66) as efficient phosphorescent material. This complex absorbs at 530 nm and exhibits weak fluorescence at 580 nm but strong phosphorescence from the triplet state at 650 nm. Triplet transfer from a host like Alq3 was assumed to follow the Dexter mechanism. Dexter-type excitation transfer is a short-range process involving the exchange of electrons. In contrast to Forster transfer, triplet exciton transfer is allowed. 

The introduction of trifluoromethyl (H2TCF3P) or phenyl groups (H2TPP) in the four meso-positions of porphin leads to relatively small and nearly identical blue shifts of the Q and B bands. However, the fluorescence lifetime is reduced by nearly one order of magnitude from H2TPP to H2TCF3P, and the fluorescence quantum yields follow the same trend (34). This is consistent with the internal heavy-atom effect to be discussed in the next section. 

The phosphorescence of porphin and its deuterated derivatives was studied in Xe matrices at 10 K (62). This significantly enhances intersystem crossing rates and increases the phosphorescence yield. It was possible to identify the 0-0 band of the phosphorescence at 790-794 nm (36 kcal/mol = 1.57 eV) in Xe matrix and the corresponding band of the fluorescence at 613 nm (46.6 kcal/mol = 2.02 eV) in Ne matrix. The same Si-Ti energy splitting for porphin and H2TPP would imply that the latter would have a triplet state energy of 33.5 kcal/mol. 

Figure 5,14. Luminescence of free-base porphine (12) in Ne (4 K) and Xe (12 K). The former is totally dominated by fluorescence (left) and the latter by phosphorescence (right) (by permission from Radziszewski et al., 1991).

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. 

Iwado, A. Mifune, M. Hazawa, T. Mukuno, T. Oda, J. Motohashi, N. Saito, Y., Peroxidase-like activity of ion exchange resin modified with metal-porphine in fluorescent flow injection analysis, Anal. Sci. 1999, 15, 841-846... 

Fluorescence quenchinfi. 277-78. 283 benzene, 265 diazabicyclooctene. 292 lO-methyiacridinium ion. 300-1 Flaorescencc speclrum. anthracene. 263 anthracene + dimclhylaniltne. 282 azulene, 273-74 perylene, 261-62 phenanthrene. 273-75 porphine. 268-69 pyrene, 280-81 Iriphenylene. 274. 276 Formaldehyde, excited stale geometry, 45. 120. 186... 

A number of reports on phthalocyanines and porphyrins have been published. Spectral diffusion and thermal recovery of spectral holes burnt into phthalocyanine doped Shpol skii systems has been examined . An absorption, emission, and thermal lensing research on carboxylated zinc phthalocyanine shows the influence of dimerization on these properties. Fourier transformation of fluorescence and phosphorescence spectra of porphine in rare gas matrices has yielded much structural and electronic state data on this compound . Exciton splitting is an effect which is seen in the spectra of covalently linked porphyrins . A ps fluorescence study of the semirigid zinc porphyrin-viologen dyad has provided evidence for two dyad conformers . Spectral diffusion in organic glasses has been measured by observing the hole recovery kinetics over the time scale of 1 to 500 ms for zinc tetrabenzoporphyrin in PMMA . 

Hennink EJ, de Haas R, Verwoerd NP et al (1996) Evaluation of a time-resolved fluorescence microscope using a phosphorescent Pt-Porphine model system. Cytometry 24 312-320... 

Innocenzi P., Kozuka H., Yoko T. Fluorescence properties of Ru(bpy) complex incorporated in sol-gel-derived silica coating films. J. Phys. Chem. B 1997 101 2285-2291 Inoue H., Iwamoto T., Makishima A., Ikemoto M., Horie K. Preparation and properties of sol-gel thin films with porphins. J. Opt. Soc. Am. 1992 B9 816-818 Ita M., Uchida Y., Matsui K. Polyaniline/silica hybrid composite gels prepared by the sol-gel process. J. Sol-Gel Sci. Tech. 2003 26 479-182... 

ProtoporiAin IX. As precursor of the most widespread iron porphins in nature, protoporphinlX, obviously, is itself found widely dispersed, although in minute amounts. It is po ble to detect traces of a porphin by observing its red fluorescence when a tissue is illuminated with ultraviolet light (around 400 mju). 

Fluorescent pigments, probably coproporphins, have been noted under certain cultural conditions in a number of bacteria, especially in mycobacteria and corynebaoteria. Coulter and Stone (21) observed the curious relation that increased porphin excretion in diphtheria paralleled increased toxin production. According to Pappenheimer (personal communication) the concentration of both compounds is influenced in the same way by varying the iron content of the medium. 

Positions and relative intensities of absorption and fluorescence bands of porphins. 

The neutral porphin has one main and three weak fluorescence bands whereas the acid form has three prominent fluorescence bands (Fig. 10). Studies of Dher6 (23,24) have revealed a whole series of still weaker fluorescence bands extending into the infrared. The solid porphins have absorption spectra shifted toward longer wave lengths, and they show emission spectra also displaced to the red (e.g., solid etioporphin. Fig. 10). 

Of all the metal porphins that have been prepared, only the magnesium, cadmium, zinc, and tin complex fluoresce, and their fluorescence is red (Table V). (In this fluorescing group may also be included the complexes with 2 H+, 2 Na+, and 2 K+.)... 

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