Porphyrins photophysical properties

Imahori H, Hagiwara K, Akiyama T, Taniguchi S, Okada T and Sakata Y 1995 Synthesis and photophysical property of porphyrin-linked fullerene Chem. Lett. 265-6... 

The reduced symmetry of the chromophore, which still contains 187t-electrons and is therefore an aromatic system, influences the electronic spectrum which shows a bathochromic shift and a higher molar extinction coefficient of the long-wavelength absorption bands compared to the porphyrin, so that the photophysical properties of the chlorins resulting from this structural alteration render them naturally suitable as pigments for photosynthesis and also make them of interest in medical applications, e.g. photodynamic tumor therapy (PDT).2... 

The zinc(II) complexes of meso-tetraphenyltetrabenzoporphyrin (38) and of meso-tetraphenyl-tetranaphthoporphyrin (39) have been prepared 173-175 some photophysical properties of this interesting series are given in Table 11176 Photooxidation of zinc(II) porphyrins causes cleavage of the macrocycle with formation of bilinone derivatives.122 206 207... 

BNCT sensitisers are designed with neutron capture in mind, but those that are porphyrin/ phthalocyanine-based may show PDT activity. An example is the disodium (or dipotassium) salt of the tetrakis-carborane ester (58) derived from 3,8-bis(l,2-dihydroxyethyl)deuteroporphyrin.298 This is water soluble and tumor selective, showing high tumor/normal brain ratios.299 Photophysical properties are similar to other water-soluble porphyrins in rat glioma cells, specific localization in mitochondria is observed.300... 

The second methodology involves direct introduction of glycosylated moieties onto a suitably functionalized meso-arylporphyrin scaffold, accessible from a natural source (protoporphyrin-IX) or by total synthesis. Several O-,133,145,146 S-,147 and N-glycoporphyrins148 (125-129) have thus been prepared (Fig. 12). Moreover, in order to explore the influence of the clustered peripheral saccharides around the porphyrin scaffolds, and to evaluate their photophysical properties, the synthesis of dodecavalent porphyrins bearing four trivalent glycodendrons via amide ligation (129) has been achieved.149... 

The first porphyrinylsugar derivatives prepared by Frank and co-workers, the bis(D-glucosyl)isohematoporphyrin 2a and bis(D-galactosyl)isohemato-porphyrin 3a, exhibit an unusual water solubility for a porphyrin derivative and also maintain the photophysical properties of their precursor 1, namely singlet oxygen production.11... 

The modification of the physical properties of some molecules as consequence of complexation with CDs is well known. Kongo et al.126 studied the TB-p-CD/porphyrine complex and observed a drastic change in the photochemical and photophysical properties of porphyrine. The conformational analysis by NMR revealed strong NOE interactions between the ligand and the internal part of the CD, in agreement with a deep insertion of the porphyrine analogue into the CD s cavity. The NOE data provided structural information to propose the 3D model of 1 2 inclusion complexes. 

Zhao, H., et al., Synthesis, characterization, and photophysical properties of covalent-linked ferrocene-porphyrin-single-walled carbon nanotube triad hybrid. Carbon, 2012. 50(13) ... 

A few examples to render tetrapyrrolic compounds less phototoxic can be found in the hterature. In one approach, carotenoid structures were employed for the synthesis of some carotenoporphyrin derivatives [92-94]. Figure 8 shows two stuctures by way of example. Due to similar photophysical properties of the two structural components, the excited triplet state of the porphyrin is quenched by the carotenoid moiety, thus inhibiting the formation of singlet oxygen, while its fluorescence capabilities are still preserved. Biodistribution studies revealed enhanced uptake into tumour tissue [39,93,95]. However, microscopy studies have shown that such compounds are associated with connective tissues in the tumors rather than with cancerous cells indicating low specificities for mahgnant transformation [96]. 

The photophysical properties of [Ru(TBP)(CO)(EtOH)], [Ru(TBP)(pyz)2], [Ru(TBP)(pyz)] (Fl2TBP = 5,10,15,20-tetra(3,5-tert-butyl-4-hydroxyphenyl)porphyrin) have been investigated by steady-state and time-resolved absorption and emission spectroscopies. The complexes are weakly luminescent, and the origins of this behavior is discussed.Transient Raman spectroscopic data have been reported for [Ru(TPP)(py)2], [Ru(TPP)(CO)(py), and [Ru(TPP)(pip)2] (pip = piperidine),and nanosecond time-resolved resonance Raman spectroscopy has been used to examine the CT excited states of [Ru(0EP)(py)2] and [Ru(TPP)(py)2]. " ... 

The present article reviews the photochemical deactivation modes and properties of electronically excited metallotetrapyrroles. Of the wide variety of complexes possessing a tetrapyrrole ligand and their highly structured systems, the subject of this survey is mainly synthetic complexes of porphyrins, chlorins, corrins, phthalocyanines, and naphthalocyanines. All known types of photochemical reactions of excited metallotetrapyrroles are classified. As criteria for the classification, both the nature of the primary photochemical step and the net overall chemical change, are taken. Each of the classes is exemplified by several recent results, and discussed. The data on exciplex and excimer formation processes involving excited metallotetrapyrroles are included. Various branches of practical utilization of the photochemical and photophysical properties of tetrapyrrole complexes are shown. Motives for further development and perspectives in photochemistry of metallotetrapyrroles are evaluated. 

The cadmium(II) complex corresponding to 9 (M = Cd n = 2) was the first texaphyrin made [6], This aromatic expanded porphyrin was found to differ substantially from various porphyrin complexes and it was noted that its spectral and photophysical properties were such that it might prove useful as a PDT agent. However, it was also appreciated that the poor aqueous solubility and inherent toxicity of this particular metal complex would likely preclude its use in vivo [29-31], Nonetheless, the coordination chemistry of texaphyrins such as 9 was soon generalized to allow for the coordination of late first row transition metal (Mn(II), Co(II), Ni(II), Zn (II), Fe(III)) and trivalent lanthanide cations [26], This, in turn, opened up several possibilities for rational drag development. For instance, the Mn(II) texaphyrin complex was found to act as a peroxynitrite decomposition catalyst [32] and is being studied currently for possible use in treating amyotrophic lateral sclerosis. This work, which is outside the scope of this review, has recently been summarized by Crow [33],... 

Harvey et al. studied the photophysical properties of macromolecules built on M-P and M-CN (isocyanide) bonds, including the metal in the backbone. (This topic is reviewed in Chapter 2. The presence of the metal atom associated with the porphyrin moiety is examined here. 

You, Y. Gibson, S. L. Hilf, R. Davies, S. R. Oseroff, A. R. Roy, I. Ohulchanskyy, T. Y. Bergey, E. J. Detty, M. R. Water soluble, core-modified porphyrins. 3. Synthesis, photophysical properties, and in vitro studies of photosensitization, uptake, and localization with carboxylic add-substituted derivatives. J. Med. Chem. 2003, 46, 3734-3747. 

The four meso positions of porphyrin have been substituted with several O-containing cycles, including benzodioxolan, benzodioxane, benzo-12-crown-4, benzo-15-crown-5, and benzo-18-crown-6 ethers (fig. 22) in an attempt to determine the influence of coordinated alkali ions on the Ybm photophysical properties (Korovin et al., 2001). The triplet state in the [Yb(10)(acac)] complexes lies in the range 13 775-13 955 cm-1 and upon excitation at 532 nm, the 5Fs/2 2F7/2 transition is seen for all five complexes. 

Sanders and coworkers have prepared a cyclic molecule featuring two zinc porphyrin donors linked to two pyromellitimide acceptors as a precursor to 32 [99, 100]. The photochemical and photophysical properties were not discussed. 

The organometallic ruthenium-arene fragments improved the aqueous solubility of the otherwise insoluble porphyrins without modifying the photophysical properties of the photosensitizer. Additionally, the presence of the ruthenium on the porphyrins facilitated uptake into melanoma cells [160]. 

Scandola F, Chiorboli C, Prodi A, Iengo E, Alessio E. Photophysical properties of metal-mediated assemblies of porphyrins. Coord Chem Rev 2006 250 1471-96. 

Ishii K, Kobayashi N. The photophysical properties of phthalocyanines and related compounds. In Kadish KM, Smith KM, Guilard R, eds. The Porphyrin Handbook. New York Academic Press, 2003 1 40. 

Many synthetic dyes such as porphyrins, acridine, thlonlne and flavin dyes have been used in photosensltlzatlon of electron transfer reactions. In the past few years several promising organometalllc compounds have been prepared as substitutes for the natural labile chlorophyll. These organometalllcs Include a variety of metals, chelated to bipyridine or porphyrin ligands ( ). The photophysical properties of these sensitizers and their potential use in artificial photosynthetic devices have been extensively reviewed ( 7, ). In particular, sensitizers such as... 

Photodynamic therapy is a powerful medical procedure that exploits the combined action of light and a photosensitizing agent for the destruction of abnormal tissues. Ideally, the photosensitizer should accumulate in the tumor cells, and the photoactivation should be carried out by irradiation with innocuous red or near-infrared (NIR) light (photodynamic window = 650-1000 nm) in order to promote the photodynamic effects only at the injured areas. Because of their suitable photochemical and photophysical properties, porphyrins and mthe-nium-polypyridine complexes are potentially useful photosensitizers for application in photodynamic therapy (217-222). 

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