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16 results on '"Gawryś, Paweł"'

1. Photochemical Hydrogen Storage with Hexaazatrinaphthylene (HATN

Author

Morawski, Olaf, Gawryś, Paweł, Sadło, Jarosław, and Sobolewski, Andrzej L.

Subjects
Physics - Chemical Physics
Abstract

When irradiated with violet light, hexaazatrinaphthylene (HATN) extracts a hydrogen atom from an alcohol forming a long-living hydrogenated species. The apparent kinetic isotope effect for fluorescence decay time in deuterated methanol (1.56) indicates that the lowest singlet excited state of the molecule is a precursor for intermolecular hydrogen transfer. The photochemical hydrogenation occurs in several alcohols (methanol, ethanol, isopropanol) but not in water. Hydrogenated HATN can be detected optically by an absorption band at 1.78 eV as well as with EPR and NMR techniques. Mass spectroscopy of photoproducts reveal di-hydrogenated HATN structures along with methoxylated and methylated HATN molecules which are generated through the reaction with methoxy radicals (remnants from alcohol splitting). Experimental findings are consistent with the theoretical results which predicted that for the excited state of the HATN-solvent molecular complex, there exists a barrierless hydrogen transfer from methanol but a small barrier for the similar oxidation of water., Comment: 14 pages, 7 figures, 2 schemes, 1 table

Published
2022
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7. Spectra and nature of the electronic states of [1]Benzothieno[3,2-b][1]benzothiophene (BTBT): Single crystal and the aggregates.

Author

Deperasińska, Irena, Banasiewicz, Marzena, Gawryś, Paweł, Morawski, Olaf, Olas, Joanna, and Kozankiewicz, Boleslaw

Subjects
SINGLE crystals, ELECTRONIC spectra, PHOSPHORESCENCE spectroscopy, UNIT cell, EXCITED states, DIMERS
Abstract

Absorption, fluorescence, and phosphorescence spectra of single crystals of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) and BTBT dispersed in frozen n-nonane, n-hexadecane, and dichloromethane matrices were studied at 5 K. Observation of a new absorption band and related changes in the fluorescence to phosphorescence intensity ratio, when the concentration of BTBT in the matrix increased above 10−4M, indicated the presence of BTBT aggregates. Quantum-chemistry calculations performed for the simplest aggregate, isolated dimer, showed that its structure is similar to the "herringbone" element in the BTBT crystal unit cell and the lowest electronic excited singlet state of the dimer has the intermolecular charge-transfer character. A qualitatively different nature of this state in dimers and in crystals, when compared with the situation in BTBT monomer [locally excited (LE) state], is associated with a decrease in the intersystem crossing yield. The structured vibronic structure of phosphorescence spectra in the studied systems indicated LE character of the triplet states. [ABSTRACT FROM AUTHOR]

Published
2021
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