Synthesis of Selenium and Tellurium Core-Modified Azuliporphyrinogens and Benziporphyrinogens and Corresponding Carbaporphyrinoids.

The synthesis of selenium and tellurium core-modified carbaporphyrinogens was carried out by the reaction of functional selenophene/tellurophene diols with azulene or a benzitripyrrane in the presence of acid. The products were obtained in moderate yields and were characterized by using 1H and 13C NMR, UV-vis, FT-IR, CV, and HRMS spectroscopic techniques. Further, oxidation of the obtained core-modified carbaporphyrinogens in the presence of DDQ in CHCl3 afforded the corresponding carbaporphyrins in good yields. Benziporphyrins showed no indication of a ring current or macrocyclic aromaticity as confirmed by using proton NMR spectroscopy, but the addition of TFA gave rise to the formation of weakly diatropic dications.

Synthesis of 21,23-selenium- and tellurium-substituted 5-porphomethenes, 5,10-porphodimethenes, 5,15-porphodimethenes, and porphotrimethenes and their interactions with mercury.

The 3+1 condensation of symmetrical 16-Selena/telluratripyrranes with symmetrical selenophene-2,5-diols/tellurophene-2,5-diols in the presence of BF3-etheratre or BF3-methanol followed by oxidation with DDQ gave 5,10-porphodimethenes, whereas the process with unsymmetrical selenophene-2,5-diols/tellurophene-2,5-diols gave 5-porphomethenes. In addition, the reaction of unsymmetrical 16-Selena/telluratripyrranes with symmetrical selenophene-2,5-diols/tellurophene-2,5-diols gave the corresponding porphotrimethenes, whereas the process with unsymmetrical selenophene-2,5-diols/tellurophene-2,5-diols gave the 5,15-porphodimethenes. The structures of different products were characterized by IR, (1)H and (13)C NMR, (1)H-(1)H COSY, CHN analysis, and mass spectrometry. The binding of mercury with the calix[4]phyrins mentioned above had been observed in the decreasing order of porphodimethenes > porphomethenes > porphotrimethenes by UV-vis and (1)H NMR spectroscopy.

Surfactant assisted self-assembly of zinc 5,10-bis (4-pyridyl)-15,20-bis (4-octadecyloxyphenyl) porphyrin into supramolecular nanoarchitectures.

The surfactant assisted self-assembly (SAS) method has been used in the formation of nanocubes, nanorods and microrods from zinc 5,10-bis (4-pyridyl)-15,20-bis (4-octadecyloxyphenyl) porphyrin. By the dropwise addition of chloroform solution of the zinc porphyrin into an aqueous solution of cetyltrimethylammonium bromide (CTAB), cuboidal nanostructures are formed at the initial stage. The nanocubes are transformed into nanorods and microrods by aging under ambient conditions. The longer nanorods with well defined edges have been formed with lower concentration of porphyrin solution whereas the shorter nanorods have been formed with higher concentration of zinc porphyrin. The synergistic effect of hydrophobic interactions by the long alkyl chains substituted on the peripheral phenyl rings of porphyrin and axial coordination of pyridyl nitrogen atoms with central zinc is mainly responsible for the formation of different nanostructures. The nanostructures were characterized by UV-visible spectra, fluorescence spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), IR spectroscopy and X-ray diffraction (XRD) pattern.

Activity-guided isolation of antioxidants from the leaves of Terminalia arjuna.

An activity-guided isolation and purification process was used to identify the l,l-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging components of the food plant (Terminalia arjuna) of Antheraea mylitta. Dry leaves of T. arjuna were extracted with different solvents and tested for their antioxidant activity against DPPH(•). The acetone-water (8:2) extract expressed strong DPPH radical-scavenging activity, and was subjected to column chromatography over silica gel. Gallic acid, apigenin, luteolin, quercetin, epicatechin, ellagic acid and 1-O-ß-galloyl glucose were isolated as active components and characterised by using different spectroscopic techniques.

Activity-guided isolation of antioxidants from the roots of Rheum emodi.

An activity-guided isolation and purification process was used to identify the DPPH free radical scavenging components of Rheum emodi. The activity-guided isolation revealed that eugenol, gallic acid, quercetin, rutin, epicatechin, desoxyrhapontigenin, rhapontigenin and mesopsin are the major phenolic compounds responsible for the antioxidant activity of the roots of R. emodi.

Electron transfer in natural and unnatural flavoporphyrins.

The development of chemical models for enzymes and their chemical and physical studies constitutes an important area of research from a scientific as well as an industrial point of view. Covalently linked flavin and porphyrin (flavoporphyrins) have attracted attention due to their applications as chemical models for flavoproteins and related enzymes. In this review, the literature has been surveyed to provide a comprehensive coverage of the synthetic methodology and characterization techniques of various types of synthetic flavoporphyrins.

9,10-Anthraquinones and other biologically active compounds from the genus Rubia.

The secondary metabolites isolated from Rubia species, their biological activities, and colouration properties have been reviewed. Over 150 chemical constituents belonging to different classes of bioactive compounds such as anthraquinones and their glycosides, naphthoquinones and glycosides, terpenes, bicyclic hexapeptides, iridoids, and carbohydrates are listed together with their source(s) and corresponding references.

Oxidation of thiols with molecular oxygen catalyzed by cobalt(II) phthalocyanines in ionic liquid.

An efficient procedure for catalyst solubility, recycling and easy product isolation in oxidation of thiols to disulfides with molecular oxygen catalyzed by cobalt(II) phthalocyanines dissolved in ionic liquid at room temperature is reported.

Effect of side chain length on the aggregation of amphiphilic 5,10,15-tris (1-methylpyridinium-4-yl)-20-[4-(alkoxy) phenyl] 21H, 23H porphyrin tritosylates.

Self-aggregation of cationic amphiphilic 5, 10, 15-tris-(1-methylpyridinium-4-yl)-20-[4-(alkoxy)phenyl]-21H, 23H porphyrin tritosylates (2a-e) with different alkoxy chain length in aqueous and binary solvent systems has been studied by UV-visible, fluorescence and (I)H NMR spectroscopy. Binary solvent, concentration, ionic strength, presence of surfactants, and temperature govern the aggregations of 2a-e. Porphyrins having side chain length more than ten carbon atoms (2c-e) form higher aggregates, such as vesicles by sonication of dimers formed initially, whereas porphyrins with lesser side chain length (2a & b) form lower aggregates only. Further, the size and the formation of vesicles have been confirmed by transmission electron microscopy (TEM) and dye entrapment experiments for 2e.

Epoxidation of alkenes with hydrogen peroxide catalyzed by iron(III) porphyrins in ionic liquids.

An efficient procedure is described for catalyst recycling and easy product isolation in alkene epoxidation with hydrogen peroxide catalyzed by water-soluble iron(III) porphyrins in environmentally benign and ambient temperature ionic liquids.