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The mechanism of the dioxygen interaction with and reduction reaction at iron α,β,γ,δ-tetra(4-pyridyl) porphyrin (FeTPyP) deposited on carbon and silver supporting electrodes was investigated with cyclic voltammetry and FTIR, UV-vis and resonance Raman spectroscopies. Results indicate a strong influence of the ligand upon the reduction electrocatalysis. Spectroelectrochemical results support a two-electron pathway resulting most probably in hydrogen peroxide as the primary reduction product.

The mode of interaction with and the mechanism of the dioxygen reduction reaction at six transition metal α,β,γ,δ-tetra(4-pyridyl)porphyrins (MeTPyPs) deposited on carbon and silver supporting electrodes were investigated with cyclic voltammetry, FTIR and UV-vis spectroscopy and resonance Raman spectroscopy. Results indicate a strong influence of both the ligand and the central metal ion upon the reduction electrocatalysis in terms of electrode overpotentials. Spectroelectrochemical results support a two-electron pathway resulting in hydrogen peroxide as the primary reduction product. A significant influence of the central ion on the vibrational behaviour and the dioxygen reduction mechanism was not found.

This paper provides a review of synthesis of the phthalocyanines containing various macrocycles at the peripheral position of the benzene rings. They are expected to be suitable to change the chemical and physical properties toward the need of technologycal applications. In addition, transition and alkali metal phthalocyanine complexes especially rare-earth bis phthalocyanines, are object of intense investigations for their unique optical and electrochemical properties. The methodology of synthesis, purification and yield varies the structural designation which is restricted and depends on the starting compounds.

The synthesis of a new ring structure, octaethylbenzochloracene (6), derived from octaethylporphycene is reported. A viable route to the benzochloracene is shown and parallels the transformation of porphyrin to benzochlorin. Octaethylbenzochloracene's spectral data shows a unique UV–vis spectrum and an interesting NMR spectrum. Unfortunately, an attempt to synthesize the analogous purpurin derivative, purpuracene (8), failed.

There is more to organic chemistry than the covalent bond. The design and synthesis of molecules, because of their particular architecture, are able to bind strongly target ions or molecules by utilizing lots of individually relatively weak non-covalent interactions has led to many novel and important applications. Examples include the transport of ions across biological membranes, the generation of unusual ionic species, such as sodium anions, the recovery of pure metals from mineral ores, and contrasting agents for magnetic resonance imaging (MRI).

Reported here is the synthesis and characterization of a new class of macrocycle that represents a hybrid between texaphyrin and calixpyrrole. These polypyrrolic macrocycles were prepared in one step by the acid-catalyzed condensation between diformyl dipyrromethanes and o-phenylenediamines in high yields. The X-ray crystal structure of one of these new “chimeras” was solved. It reveals that the diprotonated Schiff-base macrocycle has a V-shape in which one chloride anion is bound. Isothermal titration calorimetry (ITC) studies served to confirm the ability of the hybrid macrocycles to bind chloride anion in acetonitrile solution. These compounds may be useful as easy-to-make anion receptors.

In recent years, the field of porphyrin chemistry has expanded to include several new analogs of the original four pyrrole, carbon-bridged systems. This review traces the development of one such class of new macrocycles, namely Schiff-base porphyrin analogs. The review's focus is on the synthesis and properties of these new Schiff-base macrocycles that for ease of division have been divided into four classes: systems with two pyrrole rings, systems with three pyrrole or heterocyclic rings, systems with four pyrrole or heterocyclic rings, and systems with five or more pyrrole or heterocyclic rings. In addition to the role of metal ions as templating agents in the synthesis of these complexes, the rich coordination chemistry of several of the macrocycles is also discussed. X-ray crystallography has played an important role in determining the structures of many of these Schiff-base porphyrin analogs and many of the available structures have been incorporated into this review. Aromaticity of the macrocycles is discussed and has been evaluated from available electronic and NMR spectra. Finally, several potential applications of these molecules are discussed, briefly.

Regioselective bromination of methyl pyropheophorbide a at the C3²-position of the terminal double bond has been carried out as a one-pot two-step addition/elimination process. The elimination occurs with 100% stereoselectivity and bromovinyl 4 has E-configuration of the C3-double bond. The reactivity of unsaturated bromide 4 has been evaluated in the series of the Pd-catalyzed coupling reactions.

Considering the versatility of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPPF₂₀) to react with nucleophiles we highlight here the synthesis and characterization of several mono- and tetra-thiocarboxylate derivatives. The selective displacement of the para-fluorine groups in TPPF₂₀ by thiocarboxylic acids demonstrates that TPPF₂₀ is an ideal platform for the rapid formation of thiocarboxylate porphyrins. The optical and electrochemical features of the thiocarboxylate derivatives were also examined thinking on their potential use in photovoltaic devices. From their electrochemical characterization the following parameters were taken into account: (i) electronegative induced effect of the thiocarboxylate dyes owing the presence of the fluorine and sulfur atoms on the molecular structure of the porphyrin; and (ii) the free rotation and flexibility features that such S atom gives to the porphyrin relatively to the semiconductor.

Porphyrins are prominent host molecules which are widely used due to their structural characteristics and directional interaction sites. This review summarizes non-covalently bound ternary complexes of porphyrins, constructed from at least three non-identical species. Progress in supramolecular chemistry allows the creation of complex molecular machinery tools, such as rotors, motors and switches from relatively simple structures in a single self-assembly step. In the current review, we highlight the collection of sophisticated molecular ensembles including sandwich-type complexes, cages, capsules, tweezers, rotaxanes, and supramolecular architectures mediating oxygen-binding and oxidation reactions. These diverse structures have high potential to be applied in sensing, production of new smart materials as well as in medical science.

Expansion of porphyrin-like macrocycles can provide insights into the relationship between structural, optical, and electronic features. Here, we report the synthesis of a new nominally antiaromatic expanded porphyrin-like macrocycle (6) prepared via the condensation of 1,4-bis-(3,4-diethyl-2-pyrryl)benzene dialdehyde (4) with hydrazine. The absorption and emission features of this new macrocycle were compared to those of the parent bipyrrole-derived macrocycle, a system first reported in 1997. Attempts to oxidize both macrocycles (5 and 6) were unsuccessful, a failure ascribed to the steric limitations imposed by two substituents present on the $\beta$-positions on the di-substituted pyrrolic precursor. This stands in contrast to what was observed for the original bipyrrole system bearing only a single $\beta$-substituent on each of the pyrrolic moieties. The present results underscore the possible role of structure in governing electronic transitions in expanded porphyrins while highlighting the facility of hydrazine-based condensations in accessing readily large pyrrolic macrocycles.

$\beta$-Unsubstituted 5-monoazaporphyrin (MAP) copper complex 10,15,20-tritolyl-5-monoazaporphyrinato copper(II) (Cu-MAP) 3 was synthesized by reaction of 1,19-dibromotetrapyrrane with NaN₃-CuI in good yield. Following successive reactions of demetallation, metallation and bromination, the important precursor 3,7-dibromo-10,15,20-tritolyl-5-monoazaporphyrinato nickel(II) ($\beta$,$\beta \prime$-dibromo Ni-MAP) 6 was prepared smoothly. Suzuki-Miyaura coupling reactions of 6 with three organic borides resulted in the “earring” Ni-MAP 7, pyrrole bridged Ni-MAP oligomers 8 and 9, and benzene bridged Ni-MAP oligomers 10 and 11, respectively. The structures of MAPs 3, 6, 7, 8, 10 and 11 were confirmed by X-ray diffraction analysis. Optical and electrochemical studies were performed to understand their electronic properties.

The tailoring of the coordination environment around a central metal ion by changing ligands in macrocyclic complexes is one of the key approaches to monitoring their functions in various applications. Herein, two macrocyclic complexes of Co(II) transition metal ion, tetra-aza and penta-aza, were synthesized using a condensation reaction between different diamine and dicarboxylic precursors. The prepared complexes were analyzed using various characterization techniques. Further, the electrochemical behavior of both the tetra-aza and penta-aza complexes was investigated using cyclic voltammetry. The Co(II)-penta-aza-complex exhibited a quasi-reversible redox couple for Co(III)/Co(II) transition in the more anodic region as compared to Co(II)-tetra-aza-complex. According to theoretical calculations, the fifth N-coordination transferred a high electron density in the eg-orbital of Co-atom of penta-aza-complex, resulting in an anodic shift in the Co(III)/Co(II) redox potential when compared to the Co(II)-tetra-aza-complex. Furthermore, both complexes were tested for antimicrobial activity against P. aeruginosa, E. coli, S. aureus, and B. subtilis, with the results indicating that Co(II)-penta-aza-complex had higher antimicrobial activity against these bacteria than Co(II)-tetra-aza-complex. This study offers new insight into tailoring the electrochemical and biological features of macrocyclic complexes by tuning the coordination environment around the central metal ion.

Porphyrins are prominent host molecules which are widely used due to their structural characteristics and directional interaction sites. This review summarizes non-covalently bound ternary complexes of porphyrins, constructed from at least three non-identical species. Progress in supramolecular chemistry allows the creation of complex molecular machinery tools, such as rotors, motors and switches from relatively simple structures in a single self-assembly step. In the current review, we highlight the collection of sophisticated molecular ensembles including sandwich-type complexes, cages, capsules, tweezers, rotaxanes, and supramolecular architectures mediating oxygen-binding and oxidation reactions. These diverse structures have high potential to be applied in sensing, production of new smart materials as well as in medical science.