Two-photon photodynamic therapy by water-soluble self-assembled conjugated porphyrins.

Studies on two-photon absorption (2PA) photodynamic therapy (PDT) by using three water-soluble porphyrin self-assemblies consisting of ethynylene-linked conjugated bis (imidazolylporphyrin) are reviewed. 2PA cross-section values in water were obtained by an open aperture Z-scan measurement, and values were extremely large compared with those of monomeric porphyrins such as hematoporphyrin. These compounds were found to generate singlet oxygen efficiently upon one- as well as two-photon absorption as demonstrated by the time-resolved luminescence measurement at the characteristic band of singlet oxygen at 1270 nm and by using its scavenger.

Synthesis and self-organization of fluorene-conjugated bisimidazolylporphyrin and its optical properties.

A conjugated-bisimidazolylporphyrin bridged by bis(ethynylfluorene) was synthesized and organized into linear polymer through self-coordination having mean molecular weights, M(w) and M(n), of ~2.1 × 105 Da and ~1.6 × 105 Da, respectively.

Strong two-photon absorption and its saturation of a self-organized dimer of an ethynylene-linked porphyrin tandem.

The two-photon absorption properties of a self-organized dimer of a free-base and zinc(II) porphyrins tandem linked with an ethynylene group and terminated by imidazolyl and phenylethynyl groups were investigated. The self-organized dimer was found to exhibit strong two-photon absorption and furthermore the saturation of the two-photon absorption owing to the intense transition.

Fullerene- and pyromellitdiimide-appended tripodal ligands embedded in light-harvesting porphyrin macrorings.

Three new tripyridyl tripodal ligands appended with either fullerene or pyromellitdiimide moieties, named C(60)-s-Tripod, C(60)-l-Tripod, and PI-Tripod, were synthesized and introduced into a porphyrin macroring N-(1-Zn)(3) (where 1-Zn = trisporphyrinatozinc(II)). From UV-vis absorption and fluorescence titration data, the binding constants of C(60)-s-Tripod, C(60)-l-Tripod, and PI-Tripod with N-(1-Zn)(3) in benzonitrile were estimated to be 3 × 10(8), 1 × 10(7), and 2 × 10(7) M(-1), respectively. These large binding constants denote multiple interactions of the ligands to N-(1-Zn)(3).

Supramolecular organization of light-harvesting porphyrin macrorings.

Porphyrin-based supramolecular nanostructures have been produced by the self-assembly of porphyrin macrorings with three benzoic acid groups (Acid-R) on each side of the rings through cooperative carboxyl-carboxyl hydrogen bonds. Structures of the organized Acid-R were analyzed by AFM, and two clear distribution peaks were observed at 3 and 27 nm in the height-distribution histogram. From the overall assessment, the higher objects are considered to be one-dimensional structures standing vertically on the mica substrate.

Strong two-photon and three-photon absorptions in the antiparallel dimer of a porphyrin-phthalocyanine tandem.

Imidazolyl-appended phthalocyaninatozinc(II) containing an ethynylporphyrin linkage was stacked by complementary coordination into an antiparallel dimer that displayed strong nonlinear optical properties involving two-photon and three-photon absorptions.

Design of two-photon absorbing materials for molecular optical memory and photodynamic therapy.

Molecular design of two-photon absorption materials toward three dimensional high-density optical memory and highly selective photodynamic therapy at deep tissue sites is introduced. Functionality such as photochromism was attached to highly efficient 2PA materials. In the case of PDT, solubilization of the 2PA agents in water without any aggregation is important.

Single supramolecular porphyrin wires bridging gold nanoparticles.

Gold nanoparticles functionalized with imidazolylporphyrinatozinc(II)s were bridged by successive imidazole-to-zinc coordination of bidirectional porphyrinatozinc(II) units.

Energy transfer followed by electron transfer in a porphyrin macrocycle and central acceptor ligand: a model for a photosynthetic composite of the light-harvesting complex and reaction center.

A system that models a photosynthetic composite of the light-harvesting complex and reaction center is reported in which light energy collected by cyclic antenna porphyrins is transferred to a central energy-acceptor porphyrin, followed by photoinduced electron transfer to a fullerene positioned above the ring plane. Pyridyl tripodal ligands appended with bis(phenylethynyl)porphyrinatozinc(II) (ZnP-Tripod) and additional fulleropyrrolidine moieties (C(60)-ZnP-Tripod) were synthesized as the reaction center units. The tripodal ligand was strongly accommodated by the light-harvesting porphyrin macrocycle N-(1-Zn)(3) (1-Zn = trisporphyrinatozinc(II)) by using three-point coordination of pyridyl to uncoordinated porphyrinatozinc sites to afford a stable 1:1 composite.

Energy transfer among light-harvesting macrorings incorporated into a bilayer membrane.

Amphiphilic bis(imidazolyl)tris(porphyrinatozinc) complexes having omega-carboxyalkyl meso substituents were prepared. The barrel-type porphyrin macroring organized through their complementary coordination was incorporated into a liposomal bilayer membrane with orientation normal to the surface. Under the conditions concentrated in the membrane, introduction of a fullerotripyridyl ligand into the cavity of the macroring quenched fluorescence not only from the host ring itself but also from other surrounding macrorings.

Synthesis and two-photon absorption enhancement of porphyrin macrocycles.

Improving the nonlinear optical properties of organic materials through transition to macromolecular architectures of highly conjugated chromophores has been shown to be a viable strategy for generating materials suitable for TPA applications. In this study we display a simple and elegant method by which to synthesize macrocycles of porphyrin dimers. Two-photon absorption studies show 2 orders of magnitude enhancement of cross-section of the material, giving a maximum delta(2) of 10(6) GM.

Construction of giant porphyrin macrorings self-assembled from thiophenylene-linked bisporphyrins for light-harvesting antennae.

As a model of bacterial photosynthetic light-harvesting antenna, a large number of porphyrin units were organized into barrel-shaped macrorings. Two imidazolylporphyrinatozinc(II) molecules were linked through either unsubstituted thiophenes or 3,4-dioctylthiophenes 1 a and 1 b, respectively. These structures were spontaneously organized by complementary coordination of the imidazolyl to zinc and produced a series of self-assembled fluorescent polygonal macrorings under high dilution conditions.

Stepwise elongation effect on the two-photon absorption of self-assembled butadiyne porphyrins.

Butadiyne-porphyrin dimer arrays, which were generated by complementary coordination of the central zinc atom to imidazolyl followed by metathesis, were elongated stepwise and their 2PA properties were explored.

Transmembrane nanopores from porphyrin supramolecules.

A porphyrin-based nanopore was constructed through a bilayer lipid membrane (BLM). The macrocyclic porphyrin (the inner diameter = ca. 2.

Tandem cofacial stacks of porphyrin-phthalocyanine dyads through complementary coordination.

A novel straightforward methodology to organize discrete heterogeneous stacks of porphyrin and phthalocyanine employed an imidazolyl-to-zinc complementary coordination protocol for a Zn(II) phthalocyanine that contains an imidazolyl terminal with an ethynylporphyrin as a coplanar spacer. Structural elucidation was performed by means of size-exclusion chromatography, spectral titration, and NMR spectroscopy. The association constants for the complementary coordination of the heterogeneous slipped-cofacial tetrads reached extremely high values, in the order of 10(14) M(-1).

Recent advances in two-photon photodynamic therapy.

Photodynamic therapy (PDT) is a treatment for tumors and accepted in several countries in the world. Introduction of two-photon absortion (2PA) into PDT allows spatially selective treatment of cancers. Possibilities and limitations of the use of two-photon excitation in PDT are discussed, and many literatures in this area are reviewed.

Light-harvesting supramolecular porphyrin macrocycle accommodating a fullerene-tripodal ligand.

Trisporphyrinatozinc(II) (1-Zn) with imidazolyl groups at both ends of the porphyrin self-assembles exclusively into a light-harvesting cyclic trimer (N-(1-Zn)(3)) through complementary coordination of imidazolyl to zinc(II). Because only the two terminal porphyrins in 1-Zn are employed in ring formation, macrocycle N-(1-Zn)(3) leaves three uncoordinated porphyrinatozinc(II) groups as a scaffold that can accommodate ligands into the central pore. A pyridyl tripodal ligand with an appended fullerene connected through an amide linkage (C(60)-Tripod) was synthesized by coupling tripodal ligand 3 with pyrrolidine-modified fullerene, and this ligand was incorporated into N-(1-Zn)(3).

A photochromic porphyrin-perinaphthothioindigo conjugate and its two-photon absorption properties.

A porphyrin-perinaphthothioindigo conjugate having two-photon absorption cross-sections of approximately 2000 GM and approximately 700 GM for trans- and cis-isomers, respectively, was synthesized and exhibited clear photochromic behavior upon one-photon and two-photon excitation.

Ligand-induced interconversion of a coordination-organized porphyrin dimer: a potential fluorescence-based molecular memory monitor.

A novel interconversion system between less-fluorescent stacked (S) dimer and fluorescent extended (E) dimer of the monoimidazolylbisporphyrinatozinc complex was investigated. The addition of pyridine induces transformation from the S to the E dimer, whereas the addition of acetic acid and subsequent heating reverses the transformation. The interconversion rate is controlled by ligand concentration and thermal treatment.

Fine-tuning of a ferrocene[porphyrin]ITO redox cascade for efficient sequential electron transfer commenced by an S2 photoexcited special-pair mimic.

A systematic series of ferrocene/porphyrin redox cascade architectures was assembled through a slipped-cofacial porphyrin dimer on ITO electrode in optimizing the anodic photocurrent generation to perform the highest quantum yield compared to reported values on ITO electrodes.

Artificial photosynthetic systems: assemblies of slipped cofacial porphyrins and phthalocyanines showing strong electronic coupling.

This paper reviews selected types of structurally well defined assemblies of porphyrins and phthalocyanines with strong electronic coupling. Face-to-face, head-to-tail, slipped cofacial, and non-parallel dimeric motifs constructed by covalent and non-covalent bonds are compared in the earlier sections. Their molecular orientation, electronic overlap, and absorption and fluorescence properties are discussed with a view towards the development of artificial photosynthetic systems and molecular electronics.

Water-soluble self-assembled butadiyne-bridged bisporphyrin: a potential two-photon-absorbing photosensitizer for photodynamic therapy.

We have synthesized a novel, two-photon-absorbing photosensitizer for two-photon-absorption photodynamic therapy (2PA-PDT). The molecule is a butadiyne-bridged porphyrin dimer terminated with two water-soluble porphyrin monomers connected through Zn-imidazolyl self-assembly and covalently linked through olefin metathesis. It has an effective two-photon-absorption (2PA) cross-section value, sigma((2)), of 33 000+/-4600 GM with 5-ns pulses at 890 nm measured by using the open-aperture Z-scan technique.

Photoinduced electron transfer and excitation energy transfer in directly linked zinc porphyrin/zinc phthalocyanine composite.

Photoinduced electron transfer (ET) and excitation energy transfer (ENT) reactions in monomer and slipped-cofacial dimer systems of a directly linked Zn porphyrin (Por)-Zn phthalocyanine (Pc) heterodyad, ZnPc-ZnPor, were investigated by means of the picosecond and femtosecond transient absorption spectroscopies. In the dimer dyad system of two heterodyads connected through the coordination bond between two imidazolyl-substituted ZnPor bearing ZnPc, ZnPc-ZnPor(D), the rapid ENT from the ZnPor to ZnPc in the subpicosecond time region was followed by photoinduced charge separation (CS) and charge recombination (CR) with time constants of 47 and 510 ps, respectively. On the other hand in the monomer dyad system, no clear charge-separated state was observed although the CS with a time constant of 200 ps and CR with < or =70 ps were estimated.

Efficient charge injection from the S2 photoexcited state of special-pair mimic porphyrin assemblies anchored on a titanium-modified ITO anode.

A novel surface fabrication methodology has been accomplished, aimed at efficient anodic photocurrent generation by a photoexcited porphyrin on an ITO (indium-tin oxide) electrode. The ITO electrode was submitted to a surface sol-gel process with titanium n-butoxide in order to deposit a titanium monolayer. Subsequently, porphyrins were assembled as monolayers on the titanium-treated ITO surface via phosphonate, isophthalate, and thiolate groups.

Two-photon absorption properties of self-assemblies of butadiyne-linked bis(imidazolylporphyrin).

Supramolecular porphyrin self-assemblies have been prepared from butadiyne-linked bis(imidazolylporphyrin) by complementary coordination of imidazole to zinc, and their two-photon absorption (2PA) and higher-order nonlinear absorption properties were investigated over femtosecond time scales using an open-aperture Z-scan method. The self-assembled porphyrin dimer of the conjugated monozinc bisporphyrin 7D was shown to have a large 2PA cross section (7.6 x 10(3) GM, where 1 GM = 10(-50) cm(4) s molecule(-1) photon(-1)) at 887 nm.