Search results for: Helmut Görner

Items from 1 to 20 out of 63 results

article

Photoprocesses of alkyl meso-thiacarbocyanine dyes in the presence of cucurbit[7]uril

Galina V. Zakharova, Dmitrii A. Zhizhimov, Sergey K. Sazonov, Vitaly G. Avakyan, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2015 > 302 > Complete > 69-77

The effects of cucurbit[7]uril, CB7, on the photophysical processes of 3,3′-diethyl-9-methylthiacarbocyanine iodide (1), 3,3′-dihydroxyethyl-9-methylthiacarbocyanine chloride (2) and 3,3′-diethyl-5,5′-dichloro-9-ethylthiacarbocyanine p-toluene sulfonate (3) were studied in phosphate buffer (pH 6.86) mostly at room temperature. Dyes 1–3 are cationic and present as equilibrated mixtures of monomers...

article

Photoprocesses of merocyanine 540 bound to serum albumin and lysozyme

Yazhou Zhang, Helmut Görner

Journal of Molecular Structure > 2012 > 1011 > Complete > 94-98

The binding of merocyanine 540 to either lysozyme or bovine serum albumin (BSA) in aqueous solution and the related photodecomposition processes were studied. Absorption, fluorescence and trans→cis photoisomerization demonstrate a shift from free dimers to monomers upon binding to BSA, in contrast to lysozyme, where the binding appears spectroscopically less pronounced. The quantum yield (Φ _red...

article

Photophysical properties and photoreduction of N-acetyl- and N-benzoylphthalimides

László Biczók, Helmut Görner

Chemical Physics > 2012 > 392 > 1 > 10-15

The photophysical properties and photoreduction of N-acetylphthalimide (AcP) and N-benzoylphthalimide (BzP), N-3,4,5-trimethoxybenzoylphthalimide (trimethoxyBzP) and N-4-nitrobenzoylphthalimide (nitroBzP) were studied by steady-state and transient techniques. Radicals and their precursor triplet states were detected by flash photolysis. The triplet state properties of AcP and BzP were characterized...

article

Photoreduction of nitro-1,4-naphthoquinones in solution

Helmut Görner

Journal of Photochemistry & Photobiology, A: Chemistry > 2011 > 224 > 1 > 135-140

The photolysis of 2,3-dichloro-n-nitro-1,4-naphthoquinones (nitroN’Q, n: 5 and 6) was studied in benzene and acetonitrile. The triplet states of both nitroN’Qs, which can be quenched by H-atom donating solvents, e.g. 2-propanol or 1-phenylethanol, were characterized by flash photolysis. Formation and decay of nitronaphthoquinone radicals, due to H-atom transfer, were observed; the reactivities of...

article

Photooxidation of Alkaloids: Considerable Quantum Yield Enhancement by Rose Bengal‐sensitized Singlet Molecular Oxygen Generation

Helmut Görner, Zsombor Miskolczy, Mónika Megyesi, László Biczók

Photochemistry and Photobiology > 87 > 6 > 1315 - 1320

The photooxidation of sanguinarine, coralyne and berberine was studied in oxygenated alkaline methanol solutions. Rose bengal as photosensitizer significantly accelerates the process, indicating the importance of singlet molecular oxygen in the reaction mechanism. The quantum yield of sensitized oxidation was found to increase significantly with pH and reaches 0.4 for berberine at pH 13.8. The direct...

article

Peptide Release upon Photoconversion of 2‐Nitrobenzyl Compounds into Nitroso Derivatives

Koji Nakayama, Inge Heise, Helmut Görner, Wolfgang Gärtner

Photochemistry and Photobiology > 87 > 5 > 1031 - 1035

The photoinduced conversion via the aci‐nitro into the nitroso form was studied for 4,5‐dimethoxy‐2‐nitrobenzyl alcohols attached to various leaving groups: amino acids histidine (NHis) and aspartate (NAsp) as well as their fluorenylmethoxycarbonyl derivatives (FHis) and (FAsp). In addition, two peptides containing either of the two amino acids were studied, carrying the photoreactive group attached...

article

Photooxidation of lysozyme or serum albumin bound to meso-tetra-arylporphyrins

Yazhou Zhang, Helmut Görner

Dyes and Pigments > 2011 > 90 > 2 > 163-169

The photoprocesses of meso-tetra(4-sulfonatophenyl)porphyrin and meso-tetra(4-hydroxyphenyl)porphyrin were studied in the presence of lysozyme. Light-induced damage of the dyes and proteins were measured in aqueous solution at pH 4 and 8 under the exclusion of oxygen. The results were compared with those of bovine serum albumin, where virtually no photooxidation takes place. Non-covalent binding to...

article

Photoreduction and Ketone‐sensitized Reduction of Alkaloids

Helmut Görner, Zsombor Miskolczy, Mónika Megyesi, László Biczók

Photochemistry and Photobiology > 87 > 2 > 284 - 291

The photoprocesses of berberine, palmatine, coralyne, sanguinarine, flavopereirine and ellipticine were studied in several solvents. The quantum yields Φ_Δ of singlet molecular oxygen formation of berberine, palmatine and sanguinarine are moderate in dichloromethane (0.2–0.6) and much smaller in acetonitrile or trifluoroethanol. For the other alkaloids examined, Φ_Δ is rather independent of solvent...

article

Charge transfer fluorescence of trans-stryrylpyridinium iodides

Helmut Görner

Journal of Photochemistry & Photobiology, A: Chemistry > 2011 > 218 > 2-3 > 199-203

The photoprocesses of trans-1-methyl-4-[4-R-styryl]pyridinium iodide (R=H, P1) and derivatives with a cyano, a nitro and a methoxy group at the phenyl moiety, P2–P4, respectively, were studied in solution. In solvents of relatively low polarity, e.g. tetrahydrofuran, where contact ion pairs are present, the fluorescence spectrum of the styrylpyridinium is significantly red-shifted and the quantum...

article

Reduction of 4,4′‐Stilbenequinone and 4,4′‐Diphenoquinone upon Reaction with Photogenerated Radicals

Helmut Görner

Photochemistry and Photobiology > 86 > 6 > 1202 - 1207

The properties of 3,3′,5,5′‐tetra‐tert‐butyl‐4,4′‐stilbenequinone (StQ) were studied by photochemical means. Acetone, acetophenone or benzophenone was photolyzed in the presence of both StQ and a donor, such as alcohols or triethylamine. This initiated reaction of a ketyl radical with StQ to form a semiquinone radical and eventually induce a permanent bleaching due to conversion of StQ to 4,4′‐dihydroxystilbene...

article

J-aggregation of N-sulfobutyl oxacarbocyanine in binary mixtures of organic solvents

Alexander K. Chibisov, Tatyana D. Slavnova, Helmut Görner

Chemical Physics Letters > 2010 > 498 > 1-3 > 63-66

N-sulfobutyl oxacarbocyanine in binary mixtures of dimethyl sulfoxide (DMSO) as a polar solvent (0.15–2vol.%) and four less polar solvents, such as dioxane, toluene, trichloroethylene and tetrahydrofuran forms J-aggregates. Along with J-aggregates cyanine dyes form H-aggregates in the mixture of DMSO with trichloroethylene. In the mixture of DMSO with dioxane J-aggregates are formed from the monomers...

article

Photoproducts and triplet reactivity of 4′-nitro- and 2′,4′-dinitro-substituted 4-hydroxystilbenes

Helmut Görner, Mónika Megyesi, Zsombor Miskolczy, László Biczók

Journal of Photochemistry & Photobiology, A: Chemistry > 2010 > 214 > 2-3 > 188-193

The properties of triplet-excited trans-4-hydroxy-4′-nitrostilbene were studied by photochemical means. This species produces singlet molecular oxygen with a quantum yield of Φ _Δ =0.4 in benzene and 0.05 in acetonitrile. Population of the triplet state was also detected by flash photolysis. The triplet yield is substantial in benzene or toluene and small in polar solvents. The major photoprocess...

article

Nitro group photoreduction of 4-(2-nitrophenyl)- and 4-(3-nitrophenyl)-1,4-dihydropyridines

Helmut Görner

Chemical Physics > 2010 > 373 > 3 > 153-158

The photoprocesses of nifedipine, a 4-(2-nitrophenyl)-1,4-dihydropyridine, and nimodipine and nitrendipine, two 3-nitrophenyl Hantzsch-type analogues, were studied by steady-state and time-resolved methods. The intramolecular photoreduction of nifedipine into its nitrosophenyl product takes place within a few ns. The quantum yield of conversion is Φ _red =0.3 and does not depend significantly...

article

Effects of solvent polarity and hydrogen bonding on the fluorescence properties of trans-4-hydroxy-4′-nitrostilbenes

Mónika Megyesi, László Biczók, Helmut Görner, Zsombor Miskolczy

Chemical Physics Letters > 2010 > 489 > 1-3 > 59-63

The excited singlet state properties of 4′-nitro- and 2′,4′-dinitro-substituted trans-4-hydroxystilbenes were studied in various solvents. The fluorescence quantum yield (Φ _f ) of the former compound in solvents unable to form strong hydrogen bonds goes through a maximum as a function of the solvent polarity parameter ETN, reaching the highest value of 0.31 in butyronitrile. In contrast, a...

article

Photocyclization of 2,6-dichlorodiphenylamines in solution

Helmut Görner

Journal of Photochemistry & Photobiology, A: Chemistry > 2010 > 211 > 1 > 1-6

The reactions of diclofenac, meclofenamic acid and 2,6-dichlorodiphenylamine were studied by pulsed and steady-state photolysis. The primary photoprocess of diclofenac is ring closure, the quantum yield of cyclization in dichloromethane and aqueous solution is Φ _cyc =0.03 and 0.2, respectively. The results of the two related dichlorodiphenylamines are similar in the respect that the products...

article

Direct and ketone-sensitized photoconversion of 1-nitro-9,10-anthraquinone to 1-amino-9,10-anthraquinone mediated by donor radicals

Helmut Görner, Henry Gruen

Chemical Physics > 2010 > 368 > 1-2 > 20-27

The full photoreduction of 1-nitro-2-R-9,10-anthraquinone (R=H: N1, methyl: N2) was studied in benzene, acetonitrile and acetonitrile–water mixtures in the presence of 2-propanol and triethylamine (TEA). The major photoproduct is the fluorescing 1-amino-2-R-AQ (A1, A2). The quantum yield of full reduction increases with the donor concentration, approaching ΦNH2=0.1. The intermediates involved are...

article

Photocleavage of dimers of coumarin and 6-alkylcoumarins

Thomas Wolff, Helmut Görner

Journal of Photochemistry & Photobiology, A: Chemistry > 2010 > 209 > 2-3 > 219-223

The cleavage of four coumarin dimers, the syn-head-to-tail (ht) dimer of parent coumarin (syn-ht-CC1), the anti- and syn-hh dimers of 6-methylcoumarin (anti-hh-CC2 and syn-hh-CC2, respectively) and the anti-hh dimer of 6-dodecylcoumarin (anti-hh-CC3), was studied by UV–vis and IR spectroscopy and HPLC upon direct 254nm irradiation as well as sensitized excitation. The quantum yield of dimer splitting...

article

Photoinduced oxygen uptake for benzoylpyridines and dipyridylketones in aqueous solution

Helmut Görner

Journal of Photochemistry & Photobiology, A: Chemistry > 2009 > 208 > 2-3 > 141-146

The photochemical properties of 4-benzoylpyridine (4-By) and 4,4′-dipyridylketone (4,4′-Dy) were studied in air-saturated aqueous solution in the presence of formate, ascorbic acid, amines and alcohols as appropriate donors. Upon UV irradiation of these systems oxygen is consumed. The quantum yield of oxygen uptake increases with the donor concentration, approaching Φ−O2=0.2–0.8, e.g. for 4-By and...

article

Photoprocesses of chlorin e6 bound to lysozyme or bovin serum albumin

Yazhou Zhang, Helmut Görner

Dyes and Pigments > 2009 > 83 > 2 > 174-179

The ground and excited state processes of chlorin e6 in aqueous solution were studied in the presence of lysozyme and also bovine serum albumin. Non-covalent binding to proteins was analyzed using fluorescence, UV–visible and circular dichroism absorption spectroscopy. The number of binding sites, n, was 1.5–2.4 and the apparent macroscopic dissociation constant, K _d was 0.2–2.5 μM. The binding...

article

Tautomerization of lumichrome promoted by supramolecular complex formation with cucurbit[7]uril

Zsombor Miskolczy, László Biczók, Helmut Görner

Journal of Photochemistry & Photobiology, A: Chemistry > 2009 > 207 > 1 > 47-51

Addition of cucurbit[7]uril to an aqueous solution of lumichrome led to the formation of a new red-shifted band in both the absorption and fluorescence spectra indicating that binding to this rigid macrocyclic host facilitated the partial transformation into isoalloxazine-type structure. Global analysis of the results of spectrophotometric and spectrofluorometric titrations provided logK=3.92±0.06...

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Journal of Photochemistry & Photobiology, A: Chemistry (24)
The Journal of Physical Chemistry A (9)
Chemical Physics Letters (8)
Chemical Physics (5)
Journal of Photochemistry & Photobiology, B: Biology (5)
Photochemistry and Photobiology (4)
Dyes and Pigments (2)
Radiation Physics and Chemistry (2)
The Journal of Physical Chemistry B (2)
Inorganica Chimica Acta (1)
Journal of Molecular Structure (1)
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INFONA - science communication portal

Search results for: Helmut Görner

Photoprocesses of alkyl meso-thiacarbocyanine dyes in the presence of cucurbit[7]uril

Photoprocesses of merocyanine 540 bound to serum albumin and lysozyme

Photophysical properties and photoreduction of N-acetyl- and N-benzoylphthalimides

Photoreduction of nitro-1,4-naphthoquinones in solution

Photooxidation of Alkaloids: Considerable Quantum Yield Enhancement by Rose Bengal‐sensitized Singlet Molecular Oxygen Generation

Peptide Release upon Photoconversion of 2‐Nitrobenzyl Compounds into Nitroso Derivatives

Photooxidation of lysozyme or serum albumin bound to meso-tetra-arylporphyrins

Photoreduction and Ketone‐sensitized Reduction of Alkaloids

Charge transfer fluorescence of trans-stryrylpyridinium iodides

Reduction of 4,4′‐Stilbenequinone and 4,4′‐Diphenoquinone upon Reaction with Photogenerated Radicals

J-aggregation of N-sulfobutyl oxacarbocyanine in binary mixtures of organic solvents

Photoproducts and triplet reactivity of 4′-nitro- and 2′,4′-dinitro-substituted 4-hydroxystilbenes

Nitro group photoreduction of 4-(2-nitrophenyl)- and 4-(3-nitrophenyl)-1,4-dihydropyridines

Effects of solvent polarity and hydrogen bonding on the fluorescence properties of trans-4-hydroxy-4′-nitrostilbenes

Photocyclization of 2,6-dichlorodiphenylamines in solution

Direct and ketone-sensitized photoconversion of 1-nitro-9,10-anthraquinone to 1-amino-9,10-anthraquinone mediated by donor radicals

Photocleavage of dimers of coumarin and 6-alkylcoumarins

Photoinduced oxygen uptake for benzoylpyridines and dipyridylketones in aqueous solution

Photoprocesses of chlorin e6 bound to lysozyme or bovin serum albumin

Tautomerization of lumichrome promoted by supramolecular complex formation with cucurbit[7]uril

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