Porphyrin-based photosensitizers for use in photodynamic therapy

Novel linkers for linking a donor dye to an acceptor dye in an energy transfer fluorescent dye are provided. These linkers facilitate the efficient transfer of energy between a donor an acceptor dye in an energy transfer dye. One of these linkers for linking a donor dye to an acceptor dye in an energy transfer fluorescent dye has the general structure R21Z1C(O)R22R28 where R21 is a C1-5 alkyl attached to the donor dye, C(O) is a carbonyl group, Z1 is either NH, sulfur or oxygen, R22 is a substituent which includes an alkene, diene, alkyne, a five and six membered ring having at least one unsaturated bond or a fused ring structure which is attached to the carbonyl carbon, and R28 includes a functional group which attaches the linker to the acceptor dye.

Energy transfer dyes with enhanced fluorescence

Synthetic routes to multiporphyrin arrays.

From the authors' opinion, this chapter constitutes a modest extension of the seminal and inspiring contribution of Stowell and Lee on neoglycoconjugates published in this series [C P Stowell and Y C Lee, Adv Carbohydr Chem Biochem, 37 (1980) 225-281] The outstanding progresses achieved since then in the field of the "glycoside cluster effect" has witnessed considerable creativity in the design and synthetic strategies toward a vast array of novel carbohydrate structures and reflects the dynamic activity in the field even since the recent chapter by the Nicotra group in this series [F Nicotra, L Cipolla, F Peri, B La Ferla, and C Radaelli, Adv Carbohydr Chem Biochem, 61 (2007) 353-398] Beyond the more classical neoglycoproteins and glycopolymers (not covered in this work) a wide range of unprecedented and often artistically beautiful multivalent and monodisperse nanostructures, termed glycodendrimers for the first time in 1993, has been created This chapter briefly surveys the concept of multivalency involved in carbohydrate-protein interactions The topic is also discussed in regard to recent steps undertaken in glycobiology toward identification of lead candidates using microarrays and modern analytical tools A systematic description of glycocluster and glycodendrimer synthesis follows, starting from the simplest architectures and ending in the most complex ones Presentation of multivalent glycostructures of intermediate size and comprising, calix[n]arene, porphyrin, cyclodextrin, peptide, and carbohydrate scaffolds, has also been intercalated to better appreciate the growing synthetic complexity involved A subsection describing novel all-carbon-based glycoconjugates such as fullerenes and carbon nanotubes is inserted, followed by a promising strategy involving dendrons self-assembling around metal chelates The chapter then ends with those glycodendrimers that have been prepared using commercially available dendrimers possessing varied functionalities, or systematically synthesized using either divergent or convergent strategies

Design and creativity in synthesis of multivalent neoglycoconjugates.

The Clostridium acetobutylicum [FeFe]-hydrogenase HydA has been investigated as a hydrogen production catalyst in a photoelectrochemical biofuel cell. Hydrogenase was adsorbed to pyrolytic graphite edge and carbon felt electrodes. Cyclic voltammograms of the immobilized hydrogenase films reveal cathodic proton reduction and anodic hydrogen oxidation, with a catalytic bias toward hydrogen evolution. When corrected for the electrochemically active surface area, the cathodic current densities are similar for both carbon electrodes, and ∼40% of those obtained with a platinum electrode. The high surface area carbon felt/hydrogenase electrode was subsequently used as the cathode in a photoelectrochemical biofuel cell. Under illumination, this device is able to oxidize a biofuel substrate and reduce protons to hydrogen. Similar photocurrents and hydrogen production rates were observed in the photoelectrochemical biofuel cell using either hydrogenase or platinum cathodes.

[FeFe]-Hydrogenase-Catalyzed H2 Production in a Photoelectrochemical Biofuel Cell

The synthesis of some substituted tetraarylporphyrins

— Three covalently-linked porphyrin hybrid dimers were synthesized, each containing a metallotetraarylporphyrin [Zn(II), Cu(II), or Ni(II)], and a free base tetraarylporphyrin. Transfer of singlet excitation energy from the metalloporphyrin center to the free base porphyrin center was determined by measuring fluorescence properties. The Zn hybrid dimer displayed excellent intramolecular transfer of energy ( 85%) from the excited singlet state of the Zn(II) chromophore to the free base chromophore. No evidence for such transfer of the excited singlet state energy was found in the Ni(II) or Cu(II) analogues. From our experimental data, the fluorescence quantum yield of the Zn hybrid dimer was the same as for the free base monomer porphyrin (0.11; Seybold and Gouterman, 1969). Thus, the covalent attachment of another fluorescent porphyrin center effectively doubled the antenna size without decreasing the quantum yield even though the fluorescence quantum yield of the Zn(II) containing monomer was substantially less (0.03, according to Seybold and Gouterman, 1969) than that of the free base porphyrin.



The donor-acceptor distance and the rate constant for energy transfer were calculated using the Forster equation. Assuming random orientation, a donor-acceptor distance of 15 A was calculated with an associated rate constant (kci) for energy transfer of 1.9 ± 109 s–1.

John A. Anton

Papers

The synthesis of some substituted tetraarylporphyrins

Transfer of excitation energy between porphyrin centers of a covalently-linked dimer*

Synthesis of covalently linked porphyrin dimers and trimers

Synthesis of some mono, di, and trisubstituted tetraarylporphyrins