stilbenes and 4-aminostilbene

Stilbene based metal free organic dye sensitizer has been designed first time for dye sensitized solar cells applications. The geometries, electronic structures and dipole moment of the chosen 4-amino-4'-dodecyloxy-stilbene dye sensitizer has been analyzed by using Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT) calculations (based on hybrid functional B3LYP). The HOMO and LUMO energies of the dye 4-amino-4'-dodecyloxy-stilbene are -4.95 and -0.87 eV respectively calculated by using TD-DFT. To understand the conversion efficiency of the chosen dye architecture unit we selected TiO2 as a model for semiconductor. The values of polarizability and hyperpolarizability are 165. 94 and 347.74 a.u respectively based on DFT calculations. Results reveal that the selected dye sensitizer exhibits large dipole moment difference between the ground and excited state which is comparable to that of metal based dye sensitizers. Further the large dipole moment would be expected to give high photo-current conversion efficiency in practical DSSCs and also it is a promising candidate as a sensitizer for DSSC applications.

Topics: Electrons; Fluorescent Dyes; Models, Molecular; Molecular Conformation; Quantum Theory; Solar Energy; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Spectrum Analysis, Raman; Stilbenes; Thermodynamics

Measurements of active encounters between molecules in native membranes containing ingredients, including proteins, are of prime importance. To estimate rare encounters in a high range of rate constants (rate coefficients) and distances between interacting molecules in membranes, a cascade of photochemical reactions for molecules diffusing in multilamellar liposomes was investigated. The sensitised cascade triplet cis-trans photoisomerisation of the excited stilbene involves the use of a triplet sensitiser (Erythrosin B), a photochrome stilbene-derivative probe (4-dimethylamino-4'-aminostilbene) exhibiting the phenomenon of trans-cis photoisomerisation, and nitroxide radicals (5-doxyl stearic acid) to quench the excited triplet state of the sensitiser. Measurement of the phosphorescence lifetime of Erythrosin B and the fluorescence enhancement of the stilbene-derivative photochrome probe, at various concentrations of the nitroxide probe, made it possible to calculate the quenching rate constant k(q)= 1.1 x 10(15) cm2 M(-1) s(-1) and the rate constant of the triplet-triplet energy transfer between the sensitiser and stilbene probe k(T)= 1.0 x 10(12) cm2 M(-1) s(-1). These values, together with the data on diffusion rate constant, obtained by methods utilising various theoretical characteristic times of about seven orders of magnitude and the experimental rate constants of about five orders of magnitude, were found to be in good agreement with the advanced theory of diffusion-controlled reactions in two dimensions. Because the characteristic time of the proposed cascade method is relatively large (0.1 s), it is possible to follow rare collisions between molecules and free radicals in model and biological membranes with a very sensitive fluorescence spectroscopy technique, using a relatively low concentration of probes.

Topics: Antioxidants; Cell Membrane; Diffusion; Erythrosine; Fluorescent Dyes; Nitrogen Oxides; Stereoisomerism; Stilbenes; Surface Properties

A possible role of oxidative stress in producing acute toxicity in rat liver by aromatic amines and nitroarenes was tested. Oxidative stress was assessed by measuring the excretion of oxidized glutathione (GSSG) into the bile in isolated perfused livers and in female Wistar rats with cannulated bile ducts. The liver perfusion system was calibrated with t-butylhydroperoxide (t-BH) and menadione. The minimal concentration in the perfusate of t-BH necessary to observe a significant effect was 18 microM for 5 min. It was calculated that rat liver is able to cope with an extra production of about 70 nmol GSSG per min and g liver before GSSG is excreted into bile. No effect was observed when 2-aminofluorene, 2-acetylaminofluorene (AAF), trans-4-aminostilbene, and trans-4-acetylaminostilbene were added to the perfusate at 50 microM for 20 min. Moreover, 2-aminofluorene, trans-4-aminostilbene, 2-nitrofluorene and trans-4-nitrostilbene did not increase GSSG excretion when administered simultaneously with effective concentrations of t-BH. AAF was not acutely toxic, blood transaminases and lipid peroxidation were not increased with AAF doses as high as 1 mmol/kg. Since the dose rate of aromatic amines, like AAF, in feeding studies for tumor formation is about 100 times below that examined in the isolated perfused livers, it is highly unlikely that oxidative stress is generated by metabolites able to undergo redox cycling and that reactive oxygen contributes to acute toxic effects.

Topics: 2-Acetylaminofluorene; Amines; Animals; Bile; Cell Death; Female; Fluorenes; Glutathione; Liver; Oxidative Stress; Perfusion; Peroxides; Rats; Rats, Wistar; Stilbenes; tert-Butylhydroperoxide; Vitamin K

4-Amino-4'-substituted biphenyls and 4-aminostilbenes substituted in the 3' or 4' position were studied for their in vitro and in vivo genotoxicity. The in vitro mutagenicity of the biphenyls with and without S9 activation was established with Salmonella strains TA98 and TA100 and that of the stilbenes with the same strains plus TA98/1,8-DNP6. The in vivo genotoxicity assay with both series of compounds was for chromosomal aberrations in the bone-marrow cells of mice following intraperitoneal administration of the chemicals. Hammett values of substituents, partition coefficients and frontier orbital energies (ELUMO and EHOMO) of the compounds were used for correlations with mutagenicity. The Salmonella mutagenicity in TA98 and TA98/1,8-DNP6 with S9 was correlated to Hammett sigma + values for the 4-aminostilbene substituents, showing a strong trend of increasing mutagenicity with an increase in the electron-withdrawing capability of the substituent. Hydrophobicity of the stilbenes, however, had little effect on their relative mutagenicity. The 4-aminobiphenyls showed a correlation between their mutagenicity and Hammett sigma + values of their 4'-substituents in stain TA98 with S9, although the trend was not as strong as for the stilbenes. But unlike the stilbenes, TA98 mutagenicity of the biphenyls could also be correlated to hydrophobicity, and structure-activity correlations for the biphenyls was substantially improved when both sigma + and hydrophobicity data were included. For strain TA100 with S9, little correlation was found between mutagenicity of the stilbenes and any of the parameters. However, a limited correlation did exist between the mutagenicity of the biphenyls and their hydrophobicity. There was also limited correlations of the mutagenicity for the stilbenes in TA98 and TA98/1,8-DNP6 with S9 to ELUMO or EHOMO. The in vivo genotoxicity results for the biphenyls and stilbenes could not be correlated to electronic effects as for the in vitro results, nor could they be explained by hydrophobicity. However, it is interesting to note that 3'-substituted 4-aminostilbenes were all substantially more genotoxic in vivo than their corresponding 4'-substituted counterparts. The most genotoxic compound in vivo in either series was 4-aminostilbene which would not have been predicted from the in vitro results.

Topics: Aminobiphenyl Compounds; Animals; Bone Marrow; Bone Marrow Cells; Chromosome Aberrations; Liver Extracts; Mice; Microsomes, Liver; Mutagenicity Tests; Mutagens; Salmonella typhimurium; Stilbenes; Structure-Activity Relationship

Mouse lymphocytes were exposed in vitro for 2 h or in vivo for 24 h to benzidine and related aromatic amines to test for chromosome aberrations (CA) and mitotic indices. Uninduced mouse S9 was used to activate the amines for the in vitro tests to be consistent with the in vivo tests. Contrary to a previous report, no difference could be established in the genotoxicity of benzidine following activation with uninduced S9 compared to induced S9. There were concentration related increases in CA for benzidine and all the amines in vitro except for 4,4'-diaminostilbene which exhibited the greatest cellular toxicity towards cultured lymphocytes. Benzidine and its derivatives showed significant increases in CA in vivo compared to its negative control. The CA values for 4-aminostilbene were significantly higher than the other amines in both in vivo and in vitro studies. These genotoxicity results for 4-aminostilbene are consistent with our previous report of the pronounced CA effects in murine bone-marrow cells but would not be predicted from Salmonella mutagenicity tests.

Topics: Aminobiphenyl Compounds; Animals; Benzidines; Chromosome Aberrations; Liver Extracts; Lymphocytes; Male; Mice; Mice, Inbred C57BL; Microsomes, Liver; Mutagenicity Tests; Mutagens; Stilbenes; Structure-Activity Relationship

Benzidine and 12 related aromatic amines have been studied for the effects of substituent groups and pi orbital conjugation on their genotoxicity as measured by their mutagenicity in vitro with Salmonella and by chromosomal aberrations (CA) in vivo in the bone-marrow cells of mice. The in vitro studies indicated increases in mutagenicity with increases in the electron withdrawing ability of para' substituents. Mutagenicity also increases with increased conjugation as shown by the degree of planarity of the biphenyl compounds and by comparing the mutagenicities of biphenyl amines to stilbenes as well as to ethylene bridged diphenyl compounds. The relative in vitro mutagenicity results were not predictive of relative in vivo CA results. The 3 most genotoxic compounds in vivo were the conjugated amines without substituents in the para' position. The CA values for 4-aminostilbene were exceptionally high. These in vivo results indicate increased genotoxicity for benzidine analogs without substitution in the para' position.

Topics: Aminobiphenyl Compounds; Animals; Benzidines; Bone Marrow; Chromosome Aberrations; Magnetic Resonance Spectroscopy; Male; Mice; Mutagenesis; Mutagenicity Tests; Rats; Rats, Inbred Strains; Salmonella typhimurium; Stilbenes; Structure-Activity Relationship

Peroxidase (EC 1.11.1.7) activity is detected in the rat Zymbal gland, which is the target organ of trans-4-dimethylaminostilbene (trans-DAS) carcinogenicity. Measurements of peroxidase activity in ovariectomized rats show that the enzyme activity is lowered in the uterus and Zymbal gland by trans-DAS treatment and in the lungs by diethylstilboestrol (DES) treatment. In an in vitro system containing horseradish peroxidase (HRP), hydrogen peroxide and calf-thymus DNA, irreversible binding of the 3H-labelled trans-DAS metabolites 3-hydroxy-, 4'-hydroxy-, and N-hydroxy-4-acetylaminostilbene to DNA is observed. The peroxidase activity in the Zymbal gland together with the HRP-catalyzed oxidation of trans-DAS metabolites suggest a possible role for peroxidase in the organ-specific metabolic activation of trans-DAS.

Topics: Animals; Biotransformation; Carcinogens; Castration; Female; Lung; Peroxidases; Rats; Sebaceous Glands; Stilbenes

trans-4-Aminostilbene derivatives exhibit higher acute and chronic toxicity than 4-aminobibenzyl derivatives. Yet, trans-4-aminostilbene produced less methemoglobin in female Wistar rats than 4-aminobibenzyl. This cannot be explained by differences in N-oxidation since trans-4-nitrosostilbene was also less efficient than 4-nitrosobibenzyl. The fate of intravenously injected, highly and specifically 3H-labeled trans-4-aminostilbene, cis-4-aminostilbene, 4-aminobibenzyl, trans-4-nitrosostilbene and 4-nitrosobibenzyl was investigated. The results indicate that trans-4-aminostilbene and 4-aminobibenzyl are N-oxidized to a similar extent and primary activation products of trans-4-aminostilbene appear even faster in the blood. However, intermediates originating during methemoglobin formation are more reactive and covalently bind to hemoglobin 2--3 times as much with trans-stilbene as compared to bibenzyl derivatives. As a consequence the availability of these intermediates in the cyclic process and thus methemoglobin formation is reduced. Therefore, binding to hemoglobin rather than levels of methemoglobin appears to be an indicator for the availability and reactivity of some activated aromatic amine metabolites.

Topics: Animals; Blood Proteins; Chromatography, Gel; Erythrocytes; Female; Humans; In Vitro Techniques; Liver; Methemoglobin; Protein Binding; Rats; Stilbenes; Time Factors

Topics: Animals; Carcinogens; Rats; Stilbenes

Topics: Humans; Mitosis; Poisons; Stilbenes