Platinum porphyrins

Lottner, C., Bart, K.-C., Bemhart, G., Brunner, H. (2002) Hematoporphyrin-Derived Soluble Porphyrin-Platinum Conjugates with Combined Cytotoxic and Phototoxic Antitumor Activity, J. Med. Chem. 45, 2064-2078. 

Brunner H, Amdt MR, Treittinger B. Porphyrin platinum conjugates - new aims. Inorg Chim Acta 2004 357 1649-69. 

Brunner H, Schellerer K-M. New porphyrin platinum conjugates for the cytostatic and photodynamic tumor therapy. Inorg Chim Acta 2003 350 39-48. 

The dinuclear Pt complex with two porphyrin groups 214 is prepared by using 4,4 -bipy as the bridging ligand. Gombination of the porphyrin-platinum(ii) complex and metal-free porphyrin containing a pyridyl group at the 5-position enables preparation of multinuclear Pt complexes with three 215 and five 216 porphyrin units. " ... 

A sensor for nitric oxide was constructed utilizing multiwaUed carbon nanotubes that were previously modified with ethylenediamine and sonicated in a solution containing Co -TSPP. Drop cast electrodes were prepared and characterized by field-emission transmission electron microscopy, X-ray photoelectron spectroscopy and by electrochemical techniques [220]. Cyclic voltammetry, electrochemical impedance, and chronoamperometry were utilized to evaluate the electrocatalytic activity of the hybrid sensor that exhibited linear response in the 6.6 x 10 to 1.3 X 10 mol L range, with a detection limit of 6.6 x 10 mol L. Electrodes composed of porphyrins, platinum nanowires, and Nafion were proposed for photocatalytic reduction of water [221]. After an extensive search for optimization of each component and under the best conditions (—350 mV and visible light irradiation) a detectable amount of hydrogen was produced, but Nafion can diminish the diffusion of ions to the porphyrin active sites. 

With their preference for square planar coordination, palladium(II) and platinum(II) are well suited to binding to porphyrins and related N4 donor macrocycles. Therefore, Pd(octaethylporphyrin) is readily synthesized starting from the labile PhCN complex (like the platinum analogue) [92]... 

Fig. 7. Third-generation platinum-acetylide dendrimer 41 with a porphyrin core...

Gadamsetti K, Swavey S. 2006. Electrocatalytic reduction of oxygen at electrodes coated with a bimetallic cobalt(II)/platinum(II) porphyrin. J Chem Soc Dalton Trans 5530. 

Despite the potential impact of novel photosynthetic routes based on these developments, the most ambitious application remains in the conversion of solar energy into electricity. Dvorak et al. showed that photocurrent as well as photopotential response can be developed across liquid-liquid junctions during photoinduced ET reactions [157,158]. The first analysis of the output power of a porphyrin-sensitized water-DCE interface has been recently reported [87]. Characteristic photocurrent-photovoltage curves for this junction connected in series to an external load are displayed in Fig. 22. It should be mentioned that negligible photoresponses are observed when only the platinum counterelectrodes are illuminated. Considering irradiation AM 1, solar energy conversions from 0.01 to 0.1% have been estimated, with fill factors around 0.4. The low conversion... 

The first reported porphyrin complexes of platinum(IV) date from 1980 and were obtained by hydrogen peroxide oxidation of platinum(II) porphyrin complexes in an acidic medium (HC1).479 Since then oxidation of platinum(II) complexes of other porphyrins has been achieved by the same method,480 and by chlorine,481 or bromine482 oxidation. Reaction with iodine did not lead to oxidation and treatment of platinum(IV) porphyrin complexes with iodide resulted in reduction to platinum(II). 

The Soret, a and j3 bands in the visible spectra of platinum(IV) porphyrin complexes occur at longer wavelengths than their platinum(II) analogues,482 H NMR resonances are all shifted downfield,482 the 13C resonances of the a carbons are shifted upheld, and the H-195Pt and 13C-195Pt coupling constants are reduced.480 Whereas excitation of platinum(II) porphyrin complexes... 

Zhu et al. [94] reported the synthesis of Sn02 semiconductor nanoparticles by ultrasonic irradiation of an aqueous solution of SnCLj and azodicarbonamide under ambient air. They found that the sonochemically synthesized Sn02 nanoparticles improved remarkably the performance of Li ion batteries such that there was about threefold increase (from 300 to 800 mAh/g) in the reversible capacity in the first lithiation to delithiation cycles. Similarly the irreversible capacity also increased by about 70% (from 800 to 1400 mA h/g). Wang et al. [95] reported the synthesis of positively charged tin porphyrin adsorbed onto the surface of silica and used as photochemically active templates to synthesise platinum and palladium shell and... 

Table 2 summarizes these data for metal complexes of the porphyrin series which appear at present to be most relevant to PDT. Apart from the platinum(II) example, there is a reasonable correlation between this empirical 5 and stability class within each oxidation number. 

Like the palladium(II) complexes, the platinum(II) porphyrins show appreciable phosphorescence even in aqueous media at room temperature in one study,169 singlet oxygen quantum yields ranged from 0.1 to 0.9 and were strongly influenced by dimerization/aggregation. Platinum(II) 5,10,15,20-tetrakis(/>-carboxyphenyl)porphyrin and platinum(II)coproporphyrin-I ((36) for Pd read Pt) have been studied as phosphorescent labels of antibodies for use in time-resolved microscopy.189... 

Bioassays of a considerable number of drugs embodying a combination of porphyrin and cis-platin moieties in the same molecule have led to compound (43) in vitro and in vivo studies on this compound showed a phototoxicity which was additive to the cytotoxic effect of the platinum moiety.190-193... 

Optical sensors for oxygen are among the few sensors, which have found practical application for process-monitoring and clinical diagnostics. They are generally based on compounds such as platinum porphyrins or ruthenium phenanthroline derivatives (Table 17) which show a decrease in luminescence upon exposure to molecular oxygen15. 

Platinum and palladium porphyrins in silicon rubber resins are typical oxygen sensors and carriers, respectively. An analysis of the characteristics of these types of polymer films to sense oxygen is given in Ref. 34. For the sake of simplicity the luminescence decay of most phosphorescence sensors may be fitted to a double exponential function. The first component gives the excited state lifetime of the sensor phosphorescence while the second component, with a zero lifetime, yields the excitation backscatter seen by the detector. The excitation backscatter is usually about three orders of magnitude more intense in small optical fibers (100 than the sensor luminescence. The use of interference filters reduce the excitation substantially but does not eliminate it. The sine and cosine Fourier transforms of/(f) yield the following results ... 

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