Search results for: Andrzej Karocki

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article

Effect of co-ligands on photoredox pathways in Cr(III) oxalate complexes

Joanna Wiśniewska, Hasan Marai, Andrzej Karocki, Grzegorz Stopa, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2012 > 250 > Complete > 78-84

The photochemical behaviour of some mixed ligand chromium(III) complexes with amino acids, [Cr(C ₂ O ₄ ) ₂ (Aa)] ⁿ⁻ (where Aa=alanine, valine, serine, cysteine, asparagine, aspartic acid) was studied. The attention was focused on the photoredox mode, which proceeded via inner- or intramolecular pathway yielding Cr(II) species and hydrated electrons, respectively. The...

article

Photoredox reactions of Cr(III) mixed-ligand complexes

Joanna Wiśniewska, Hasan Marai, Andrzej Karocki, Konrad Szaciłowski, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2010 > 209 > 2-3 > 121-127

Irradiation of chromium(III) complexes with oxalate and pyridinedicarboxylate ligands (pda=2,3-, 2,4-, or 2,5-dicarboxylate) leads to diverse behaviors, dictated by light energy, presence of oxygen and the ligand nature. Irradiation within the MC bands is unaffected by O ₂ and results in ligand substitution. The LMCT excitation is effective only when oxalate is coordinated to Cr(III); then...

article

Verteporfin, photofrin II, and merocyanine 540 as PDT photosensitizers against melanoma cells

Patrycja Nowak-Sliwinska, Andrzej Karocki, Martyna Elas, Anna Pawlak, more

Biochemical and Biophysical Research Communications > 2006 > 349 > 2 > 549-555

The efficiency of photodynamic effect (PDE) for Photofrin II (PfII), Verteporfin, and Merocyanine 540 (MC540) was compared against neoplastic cells. Triplet state lifetimes and singlet molecular oxygen quantum yields were correlated with biological effect. PfII triplet lifetime was two times longer than that of Verteporfin, however, its singlet molecular oxygen quantum yield was two times lower in...

article

Effect of temperature and solvent polarity on the CT fluorescence

Marek Mac, Andrzej Danel, Anna Wisła, Andrzej Karocki, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2006 > 180 > 1-2 > 88-100

Three dyes containing the 1H-pyrazolo[3,4-b]quinoxaline moiety have been synthesized and investigated as novel fluorophores exhibiting charge transfer fluorescence. The effect of changing temperature and solvent polarity on CT fluorescence of these compounds was investigated by steady-state and time-resolved fluorescence methods. Detailed investigation of the influence of temperature on charge transfer...

article

A mechanistic study

Przemysław Kocot, Andrzej Karocki, Zofia Stasicka

Journal of Photochemistry & Photobiology, A: Chemistry > 2006 > 179 > 1-2 > 176-183

The Fe(III) photoreduction in the EDTA complexes studied by pulse photolysis and continuous irradiation revealed that LMCT excitation is followed by reaction of the primary photoproduct with the parent complex, generating intermediate species formulated as [(H ₂ O)(EDTA ⁺ )Fe ^II (μ-OH _x )Fe ^III EDTA] ^x−4 . The presence of molecular oxygen is of crucial...

article

Effects of heavy central metal on the ground and excited states of chlorophyll

Agnieszka Drzewiecka-Matuszek, Agnieszka Skalna, Andrzej Karocki, Grażyna Stochel, more

JBIC Journal of Biological Inorganic Chemistry > 2005 > 10 > 5 > 453-462

Chlorophylls, owing to their adjustable π-electron system and intense, well-separated electronic transitions, can serve as convenient intrinsic spectroscopic probes of ligand–metal center interactions. They are also interesting for their photosensitizing properties. In order to examine the heavy-atom effects on the chlorophyll triplet state, a key intermediate in chlorophyll–photosensitized reactions,...

article

Photoredox behaviour of the Cr-EDTA complex and its environmental aspects

Paweł Cieśla, Andrzej Karocki, Zofia Stasicka

Journal of Photochemistry & Photobiology, A: Chemistry > 2004 > 162 > 2-3 > 537-544

Polychromatic radiation from a mercury lamp or light mimicking the sunlight (λ>=300nm) is able to initiate an innersphere electron transfer in the [Cr ^I ^I ^I EDTA(OH)] ² ^- complex, leading to formation of a Cr(II) centre and the EDTA radical. Under defined conditions (pH >= 7, O ₂ in excess over the Cr(II) concentration) the photoreduction is followed by thermal...

article

Mechanism of photochemical reduction of chromium(VI) by alcohols and its environmental aspects

Piotr Mytych, Andrzej Karocki, Zofia Stasicka

Journal of Photochemistry & Photobiology, A: Chemistry > 2003 > 160 > 3 > 163-170

The idea of photochemical abatement of the Cr(VI) pollution has been verified by investigating the photoreduction mediated by aliphatic alcohols under conditions mimicking the environmental ones. Effects of the alcohol nature, pH and presence of oxygen are analysed. The time-resolved spectra are used to follow the generation of the transient chromium Cr(V), Cr(IV) and Cr(II) species and the R ...

article

Photochemistry of the [Fe(CN)5N(O)SR]3− complex

Konrad Szaciłowski, Janusz Oszajca, Andrea Barbieri, Andrzej Karocki, more

Journal of Photochemistry and Photobiology A: Chemistry > 2001 > 143 > 2-3 > 99-108

Photochemical behaviour of the title complex (RS⁻=mercaptosuccinate) was defined as photodissociation and photooxidation–substitution reactions induced by the MLCT transition. The stable products as well as shortly lived intermediate species were identified and characterised by ESR and fast UV/VIS spectroscopic methods. The photodissociation of excited [Fe(CN)₅N(O)SR)]³⁻ (Scheme 1Scheme 1, path a)...

article

Photochemistry of [(η ⁵ -C ₅ H ₅ )Ru(CO) ₂ ] ₂ in polar and non-polar solvents

Wojciech Macyk, Anna Herdegen, Andrzej Karocki, Grażyna Stochel, more

Journal of Photochemistry & Photobiology, A: Chemistry > 1997 > 103 > 3 > 221-226

The photochemistry of bridged and non-bridged isomers of the title complex was studied in various solvents by flash photolysis and continuous irradiation at different wavelength regions. Reactive decay of the excited non-bridged isomer produced either a polymer (in neat non-polar solvents) or monomeric [CpRu(CO) ₂ Cl] complex (in non-polar solvents containing CCl ₄ ) via homolytic...

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