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Titolo:
Time-resolved spectroscopy of sulfur- and carboxy-substituted N-alkylphthalimides
Autore:
Gorner, H; Griesbeck, AG; Heinrich, T; Kramer, W; Oelgemoller, M;
Indirizzi:
Max Planck Inst Strahlenchem, D-45413 Mulheim, Germany Max Planck Inst Strahlenchem Mulheim Germany D-45413 13 Mulheim, Germany Univ Cologne, Inst Organ Chem, D-50939 Cologne, Germany Univ Cologne Cologne Germany D-50939 rgan Chem, D-50939 Cologne, Germany
Titolo Testata:
CHEMISTRY-A EUROPEAN JOURNAL
fascicolo: 7, volume: 7, anno: 2001,
pagine: 1530 - 1538
SICI:
0947-6539(20010401)7:7<1530:TSOSAC>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
SINGLET MOLECULAR-OXYGEN; LASER FLASH-PHOTOLYSIS; CONTAINING AMINO-ACIDS; AQUEOUS-SOLUTION; 4-CARBOXYBENZOPHENONE-SENSITIZED PHOTOOXIDATION; ELECTRON-TRANSFER; KETYL RADICALS; PHOTOPHYSICAL PROPERTIES; PHTHALOYL DERIVATIVES; ABSORPTION-SPECTRA;
Keywords:
electron transfer; photochemistry; photocyclization; phthalimide; quantum yields;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
57
Recensione:
Indirizzi per estratti:
Indirizzo: Gorner, H Max Planck Inst Strahlenchem, Stiftstr 34-36, D-45413 Mulheim, Germany Max Planck Inst Strahlenchem Stiftstr 34-36 Mulheim Germany D-45413
Citazione:
H. Gorner et al., "Time-resolved spectroscopy of sulfur- and carboxy-substituted N-alkylphthalimides", CHEM-EUR J, 7(7), 2001, pp. 1530-1538

Abstract

The photophysical and photochemical properties of N-phthaloylmethionine (1), S-methyl-N-phthaloyl-cysteine methyl ester (2) and N-phthaloyltranexamicacid (3) were studied by time-resolved UV/Vis spectroscopy, using laser pulses at 248 or 308 nm. The quantum yield of fluorescence is low (Phi (f)< 10(-2)) for 1-3 in fluid and glassy media, whereas that of phosphorescence is large (0.3-0.5) in ethanol at - 196<degrees>C. The triplet properties were examined in several solvents, at room temperature and below. The spectra and decay kinetics are similar, but the population of the pi,pi* triplet state, as measured by T-T absorption, is much lower for 1 and 2 than for 3 orN-methyltrimellitimide (5') at ambient temperatures. The quantum yield (Phi (Delta)) of singlet molecular oxygen O-2((1)Delta (g)) formation is substantial for 3 and 5' in several air- or oxygen-saturated solvents at room temperature, but small for 2 and 1. The quantum yield of decomposition is substantial (0.2-0.5) for 3 and small (< 0.05) for 2 and 1. It is postulated that photoinduced charge separation in the spectroscopically undetectable (3)n,<pi>* state may account for the cyclization products of 1 and 2. In aqueous solution, this also applies for 3, whereas in organic solvents cyclization involves mainly the lower lying (3)pi,pi* state. Triplet acetone, acetophenone and xanthone are quenched by 1-3 in acetonitrile; the rate constantis close to the diffusion-controlled limit, but smaller for benzophenone. While the energy transfer from the triplet ketone occurs for 3, a major contribution of electron transfer to the N-phthalimide derivative is suggestedfor 1 and 2, where the radical anion of benzophenone or 3-carboxybenzophenone is observed in alkaline aqueous solution.

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Documento generato il 29/09/20 alle ore 00:28:19