- Supramolecular crystal chemistry with porphyrin tinkertoys. Hydrogen-bonding and coordination networks with the chair and table conformers of tetra(3-carboxyphenyl)porphyrin
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This study explores further the supramolecular reactivity of the meso-tetra(3-carboxyphenyl)porphyrin (T3CPP) building block in the context of crystal engineering. T3CPP has coordination as well as hydrogen bonding tetradentate functionalities, and exhibits orientational versatility of the 3-carboxylic substituents with respect to the porphyrin core; chair- and table-like conformers have been expressed in this study. In the chair variant of T3CPP, two adjacent carboxylic functions are oriented upward and the other two downward, while in the table isomer all four carboxylic arms are oriented in the same direction. Solvothermal reactions of the T3CPP with cadmium and zinc ions afforded metalation of the porphyrin core and hybrid coordination compounds with uniquely interesting and novel architectures. This includes a discrete 4:2 Cd/Zn:porphyrin assembly (4), where the four metal ions link (as mononuclear connectors) between the two metalloporphyrins (present in a table conformation) into a molecular-box, as well as coordination polymers of one-dimensional (5) and two-dimensional (6-8) connectivity. Additional experiments led to the syntheses of hydrogen-bonded networks between the T 3CPP/Co-T3CPP moieties (given in the chair conformation) and various amine ligands present in the reaction mixtures (1-3). These were associated with either partial or full proton-transfer from the porphyrin tetra-acid to the amine species to further stabilize the supramolecular networking by added electrostatic attraction. The above findings confirm that the T3CPP scaffold may effectively engage in diverse supramolecular constructs, through direct multiple-coordination to metal-ion connectors, as well as in extended hydrogen-bonding networks. While the occurrence of the table conformer of T3CPP in the above context has been observed here for the first time, new supramolecular materials are expected to emerge in the future with the still missing tetrahedral form (with the carboxylic substituents oriented in alternating directions around the porphyrin macrocycle) of this versatile ligand.
- Lipstman, Sophia,Goldberg, Israel
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- Light-induced electron transfer over distances of 5, 10, and 15 A within water-filled yoctowells
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A small series of variable-depth yoctowell cavities with functional walls on aminated silica particles and gold electrodes has been established. The dimensions of the gaps formed were 2.2 nm in diameter with varying functional depths of 5, 10, and 15 A, depending on the length of bolaphiles applied and the position of the positive rim; these gaps were prepared through a Michael addition of the incorporated ene-amide groups. Using this construct and electrostatic interactions between the positive rim and anionic quinones as a means of immobilization, a porphyrin-quinone dyad system has been prepared. The distance between the donor and acceptor was changed systematically in aqueous solution, whilst maintaining a similar environment in each case. Upon photoexcitation of the porphyrin, efficient electron transfer occurs between the porphyrin and quinone units in a distance-dependent manner on the nanosecond timescale.
- Bhosale, Sheshanath V.,Hackbarth, Steffen,Langford, Steven J.,Bhosale, Sidhanath V.
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- A chromatography-free synthesis of meso-Tetrakis(4-formylphenyl) porphyrin and meso-Tetrakis(3-formylphenyl) porphyrin: Versatile synthons in supramolecular and macromolecular chemistry
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A facile synthetic strategy was developed for the synthesis of meso-Tetrakis(4-formyl-phenyl)porphyrin and meso-Tetrakis(3-formylphenyl)porphyrin from commercially available starting materials. This method gives facile access to practical amounts of these synthons in high purity and good overall yield, without employing laborious chromatographic separations. The reduction of the respective carboxylic acid-functionalized porphyrins by LiAlH4 afforded the tetra(benzylalcohol)porphyrin intermediates, subsequently utilized in a Parikh-Doering oxidation to selectively afford the desired tetraformylated products. The inherent ease of synthesis of these porphyrin building blocks provides a convenient pathway for the synthesis of various macromolecular and supramolecular architectures for applied chemical technologies.
- De Bruin, Bas,Mathew, Simon,Meeus, Eva J.,Mouarrawis, Valentinos,Reek, Joost
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- Porphyrin n-pincer pd(Ii)-complexes in water: A base-free and nature-inspired protocol for the oxidative self-coupling of potassium aryltrifluoroborates in open-air
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Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetra-sodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.
- Hanafiah, Marlia M.,Lakkaboyana, Sivarama Krishna,Lakshmidevi, Jangam,Marella, Ravi Kumar,Naidu, Bandameeda Ramesh,Prasad, Sana Siva,Venkateswarlu, Katta
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- Silylation improves the photodynamic activity of tetraphenylporphyrin derivatives in vitro and in vivo
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The effects of silyl and hydrophilic groups on the photodynamic properties of tetraphenylporphyrin (TPP) derivatives have been studied in vitro and in vivo. Silylation led to an improvement in the quantum yield of singlet oxygen sensitization for both sulfo and carboxy derivatives, although the silylation did not affect other photophysical properties. Silylation also improved the cellular uptake efficiency for both sulfo and carboxy derivatives, enhancing the in vitro photodynamic activity of the photosensitizer in U251 human glioma cells. The carboxy derivative (SiTPPC4) was found to show higher cellular uptake efficiency and in vitro photodynamic activity than the corresponding sulfo derivative (SiTPPS4), which indicates that the carboxy group is a more promising hydrophilic group than the sulfo group in the silylated porphyrin. SiTPPC4 was found to show high selective accumulation efficiency in tumors, although almost no tumor selectivity was observed for the nonsilylated porphyrin. The concentration of SiTPPC4 in tumors was 13 times higher than that in muscle 12 h after drug administration. We also studied tumor response after treatment and found that silylation enhanced in vivo photodynamic activity significantly. SiTPPC 4 shows higher photodynamic activity than NPe6 with white light irradiation. Improved photosensitizers: Silylation improves the quantum yield of singlet oxygen sensitization, cellular uptake efficiency, and selective accumulation efficiency in tumors. As a result of these improvements, silylation significantly enhances photodynamic activity (see figure). The results of this work suggest that silylation is a promising strategy for improving photosensitizers for photodynamic therapy.
- Horiuchi, Hiroaki,Hosaka, Masahiro,Mashio, Hiroyuki,Terata, Motoki,Ishida, Shintaro,Kyushin, Soichiro,Okutsu, Tetsuo,Takeuchi, Toshiyuki,Hiratsuka, Hiroshi
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supporting information
p. 6054 - 6060
(2014/05/20)
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