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Oxazine Rings (oxazine + ring)

Distribution by Scientific Domains
Chemistry50%

Selected Abstracts

Photochromic Polymers Based on the Photoinduced Opening and Thermal Closing of [1,3]Oxazine Rings

ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009
Massimiliano Tomasulo
Abstract Two macromolecular constructs incorporating a single polymer backbone with multiple photochromic side chains are developed. Both systems are prepared from preformed photochromic [1,3]oxazines after the ring-opening polymerization of their norbornene appendages. In solution, UV illumination of these polymers opens the [1,3]oxazine rings in their side chains in less than 6,ns and with a quantum yield of 0.09 in both instances. The photogenerated species incorporate a 4-nitrophenolate chromophore, and hence, their formation is accompanied by the appearance of an intense band in the visible region of the absorption spectrum. The photoproducts revert spontaneously to the original state with first-order kinetics in microseconds. Furthermore, both photochromic polymers tolerate hundreds of switching cycles with no sign of degradation, even in the presence of molecular oxygen. Thus, this design logic and choice of functional building blocks can translate into the realization of innovative photoresponsive materials with excellent photochromic performance. [source]

Eight 7-benzyl-3- tert -butyl-1-phenylpyrazolo[3,4- d]oxazines, encompassing structures containing no intermolecular hydrogen bonds, and hydrogen-bonded structures in one, two or three dimensions

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009
Juan C. Castillo
7-Benzyl-3- tert -butyl-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C22H25N3O, (I), and 3- tert -butyl-7-(4-methylbenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H27N3O, (II), are isomorphous in the space group P21, and molecules are linked into chains by C,H...O hydrogen bonds. In each of 3- tert -butyl-7-(4-methoxybenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H27N3O2, (III), which has cell dimensions rather similar to those of (I) and (II), also in P21, and 3- tert -butyl-1-phenyl-7-[4-(trifluoromethyl)benzyl]-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H24F3N3O, (IV), there are no direction-specific interactions between the molecules. In 3- tert -butyl-7-(4-nitrobenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C22H24N4O3, (V), a combination of C,H...O and C,H...N hydrogen bonds links the molecules into complex sheets. There are no direction-specific interactions between the molecules of 3- tert -butyl-7-(2,3-dimethoxybenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C24H29N3O3, (VI), but a three-dimensional framework is formed in 3- tert -butyl-7-(3,4-methylenedioxybenzyl)-1-phenyl-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C23H25N3O3, (VII), by a combination of C,H...O, C,H...N and C,H...,(arene) hydrogen bonds, while a combination of C,H...O and C,H...,(arene) hydrogen bonds links the molecules of 3- tert -butyl-1-phenyl-7-(3,4,5-trimethoxybenzyl)-6,7-dihydro-1H,4H -pyrazolo[3,4- d][1,3]oxazine, C25H31N3O4, (VIII), into complex sheets. In each compound, the oxazine ring adopts a half-chair conformation, while the orientations of the pendent phenyl and tert -butyl substituents relative to the pyrazolo[3,4- d]oxazine unit are all very similar. [source]

Photochromic Polymers Based on the Photoinduced Opening and Thermal Closing of [1,3]Oxazine Rings

ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009
Massimiliano Tomasulo
Abstract Two macromolecular constructs incorporating a single polymer backbone with multiple photochromic side chains are developed. Both systems are prepared from preformed photochromic [1,3]oxazines after the ring-opening polymerization of their norbornene appendages. In solution, UV illumination of these polymers opens the [1,3]oxazine rings in their side chains in less than 6,ns and with a quantum yield of 0.09 in both instances. The photogenerated species incorporate a 4-nitrophenolate chromophore, and hence, their formation is accompanied by the appearance of an intense band in the visible region of the absorption spectrum. The photoproducts revert spontaneously to the original state with first-order kinetics in microseconds. Furthermore, both photochromic polymers tolerate hundreds of switching cycles with no sign of degradation, even in the presence of molecular oxygen. Thus, this design logic and choice of functional building blocks can translate into the realization of innovative photoresponsive materials with excellent photochromic performance. [source]

Studies on the resonance Raman spectra of polyaniline obtained with near-IR excitation,

JOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2008
Gustavo M. do Nascimento
Abstract The effects of near-IR (NIR) laser power over the Raman spectra of poly(aniline) emeraldine salt (PANI-ES) and base (PANI-EB) were investigated. The reasons for the existence of several bands from 1324 to 1500 cm,1 in the Raman spectra of poly(aniline) obtained at NIR region were also studied. The bands from 1324 to 1375 cm,1 were associated to ,CN of polarons with different conjugation lengths and the bands from 1450 to 1500 cm,1 in Raman spectra of PANI emeraldine and pernigraniline base forms were correlated to ,CN modes associated with quinoid units having different conjugation lengths. The increase of laser power at 1064.0 nm causes the deprotonation of PANI-ES and the formation of cross-linking segments having phenazine and/or oxazine rings. For PANI-EB only a small spectral change is observed when the laser power is increased, owing to the low absorption of this form in the NIR region. Copyright © 2007 John Wiley & Sons, Ltd. [source]