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Five isomers of monomeric cytosine and their interconversions induced
Lapinski, Leszek; Igor Reva, Igor Reva; Nowak, Maciej J.; Fausto, RuiPhotoisomerization processes involving five isomers of cytosine were induced by narrowband tunable UV irradiation of matrix-isolated monomers of the compound. Irradiation of an argon matrix containing cytosine monomers with UV l = 313 nm laser light resulted in syn2anti photoisomerizations between the two imino–oxo forms, whereas the substantially more populated amino–hydroxy and amino–oxo forms stayed intact. ...
Positive Identification of UV-Generated, Non-Hydrogen-Bonded Isomers of o-Hydro...
Lapinski, Leszek; Rostkowska, Hanna; Reva, Igor; Fausto, Rui; Nowak, Maciej J.Non-hydrogen-bonded isomers were photogenerated by UV (λ > 335 nm) irradiation of o-hydroxybenzaldehyde (salicylaldehyde) and o-hydroxyacetophenone monomers isolated in low-temperature Ar matrixes. These photoisomerizations were found to be photoreversible. Upon shorter wavelength (λ > 235 nm or λ > 270 nm) UV irradiation, the initial forms of the compounds (with intramolecular hydrogen bonds) were partially re...
NIR-laser-induced selective rotamerization of hydroxy conformers of cytosine
Lapinski, Leszek; Nowak, Maciej J.; Reva, Igor; Rostkowska, Hanna; Fausto, RuiThe relative populations of two amino-hydroxy conformers of cytosine, differing in rotation of the OH group by 180°, were selectively and repeatedly manipulated with narrowband, near-infrared laser light. For cytosine monomers isolated in a low-temperature Ar matrix, laser irradiations at 7013 cm−1 and at 7034 cm−1 were found to induce effective transformations of the two conformers into each other.
Photoinduced oxidation of triphenylphosphine isolated in a low-temperature oxyg...
Reva, Igor; Lapinski, Leszek; Nowak, Maciej J.http://www.sciencedirect.com/science/article/B6TFN-4TXF81D-3/2/a7ee21821936ceab2970c58d4ce846aa
Photoinduced transformation of matrix-isolated methyl 2-pyrone-3-carboxylate in...
Reva, Igor; Nowak, Maciej J.; Lapinski, Leszek; Fausto, RuiPhotochemical transformations of methyl 2-pyrone-3-carboxylate (mp3c) were studied by matrix-isolation technique. The dominating primary photoreaction induced by UV (λ > 295 nm) light was α-bond cleavage leading to open-ring aldehyde–ketene. Another reaction characteristic of α-pyrones, isomerisation to the Dewar form, did not occur for mp3c. The ring-opening photoreaction was followed by intramolecular hydroge...
Dimer formation in nicotinamide and picolinamide in the gas and condensed phase...
Borba, Ana; Albrecht, Merwe; Gómez-Zavaglia, Andrea; Lapinski, Leszek; Nowak, Maciej J.; Suhm, Martin A.; Fausto, RuiAggregation of nicotinamide (3-pyridine-carboxamide; NA) and picolinamide (2-pyridine-carboxamide; PA) has been investigated by matrix-isolation, supersonic jet and neat solid state infrared spectroscopy, complemented by DFT(B3LYP)/6-311++G(d,p) calculations. For both compounds, the most stable dimeric structure was shown to be the centrosymmetric dimer where two monomers in their most stable forms establish tw...
Double-Proton-Transfer Processes in Dithiooxamide: UV-Induced Dithione → Dithi...
Lapinski, Leszek; Rostkowska, Hanna; Khvorostov, Artem; Yaman, Müjgan; Fausto, Rui; Nowak, Maciej J.Dithiooxamide [rubeanic acid, NH2C(S)C(S)NH2)] monomers were studied by FTIR spectroscopy combined with the low-temperature matrix-isolation technique. The most stable dithione−diamino tautomer of the compound was exclusively observed in argon matrixes immediately after deposition. Upon UV (λ > 345 nm) irradiation the dithione−diamino form transformed, by a double-proton transfer, into the dithiol−diimino tauto...
Photoisomerization reactions of 4-methoxy- and 4-hydroxy-6-methyl-α-pyrones: An...
Breda, Susana; Lapinski, Leszek; Fausto, Rui; Nowak, Maciej J.Photoisomerization reactions were studied for 4-methoxy- and 4-hydroxy-6-methyl-α-pyrones isolated in low-temperature Ar matrices. Two types of photoproducts: Dewar valence isomer and conjugated aldehyde–ketene were photogenerated upon UV irradiation of the matrix-isolated compounds. After prolonged irradiation practically all the initial material was converted to the corresponding Dewar isomers, whereas the po...
Photochemical Ring-Opening Reaction in 2(1H)-Pyrimidinones: A Matrix Isolation...
Lapinski, Leszek; Rostkowska, Hanna; Khvorostov, Artem; Fausto, Rui; Nowak, Maciej J.Photoreactions induced by UV-B (290−320 nm) irradiation were studied for 1-methyl-2(1H)-pyrimidinone and 1-methylcytosine monomers isolated in low-temperature inert gas matrixes. A Norrish type I α-cleavage reaction leading to open-ring conjugated isocyanate was observed for 1-methyl-2(1H)-pyrimidinone. The structure of the photoproduct was identified by comparison of its experimental IR spectrum with the spect...
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