Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis
| ISSN: |
0047-2670
|
|---|---|
| Source: |
Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
|
| Topics: |
Chemistry and Pharmacology
|
| Type of Medium: |
Electronic Resource
|
| URL: |
| _version_ | 1798291504143269888 |
|---|---|
| autor | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. |
| autorsonst | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. |
| book_url | http://linkinghub.elsevier.com/retrieve/pii/0047-2670(85)87048-9 |
| datenlieferant | nat_lic_papers |
| fussnote | The primary processes in the photoisomerization of spiro[3-methyl-8-methoxy-6-nitro-2H(1)-benzopyran-2,2',3',3'-dimethylpiperid ine] (Me-SP) in toluene were studied from 273 to 323 K by means of nanosecond laser photolysis using the third harmonic (353 nm) of a neodymium-glass laser as the excitation light (pulses with a full width at half-maximum of 6 ns). The results indicate that benzopyran ring opening in Me-SP occurs in both the excited singlet state and the lowest triplet state. Photoisomerization in Me-SP does not lead to an all-trans isomer because of steric hindrance due to the two methyl groups in the 3' position and the one methyl group in the 3 position, but instead leads to a cisoid isomer X characterized by a lifetime of about 3 s at 297 K and an absorption centred at 440 nm. X is formed exclusively from the excited singlet state of Me-SP. Two triplet species, one of which was formed from the other, were detected. Their lifetimes were 25 ns and 2.2 μs respectively at 297 K. The first triplet T was assigned to the lowest triplet state of Me-SP and the second triplet ^3Y to the lowest triplet state of a species (different from X) formed just after Cz.sbnd;O bond rupture. The triplet ^3Y relaxes towards the ground state of Me-SP. The activation energy of the T -〉 ^3Y process is about 5 kcal mol^-^1. |
| hauptsatz | hsatz_simple |
| identnr | NLZ174721374 |
| issn | 0047-2670 |
| journal_name | Journal of Photochemistry |
| materialart | 1 |
| package_name | Elsevier |
| publikationsort | Amsterdam |
| publisher | Elsevier |
| reference | 28 (1985), S. 547-558 |
| search_space | articles |
| shingle_author_1 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. |
| shingle_author_2 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. |
| shingle_author_3 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. |
| shingle_author_4 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. |
| shingle_catch_all_1 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis 0047-2670 00472670 Elsevier |
| shingle_catch_all_2 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis 0047-2670 00472670 Elsevier |
| shingle_catch_all_3 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis 0047-2670 00472670 Elsevier |
| shingle_catch_all_4 | Kellmann, A. Lindqvist, L. Monti, S. Tfibel, F. Guglielmetti, R. Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis 0047-2670 00472670 Elsevier |
| shingle_title_1 | Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis |
| shingle_title_2 | Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis |
| shingle_title_3 | Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis |
| shingle_title_4 | Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis |
| sigel_instance_filter | dkfz geomar wilbert ipn albert fhp |
| source_archive | Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 |
| timestamp | 2024-05-06T08:33:40.317Z |
| titel | Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis |
| titel_suche | Primary processes in the photochromism of a sterically crowded piperidinospiropyran studied by nanosecond laser photolysis The primary processes in the photoisomerization of spiro[3-methyl-8-methoxy-6-nitro-2H(1)-benzopyran-2,2',3',3'-dimethylpiperid ine] (Me-SP) in toluene were studied from 273 to 323 K by means of nanosecond laser photolysis using the third harmonic (353 nm) of a neodymium-glass laser as the excitation light (pulses with a full width at half-maximum of 6 ns). The results indicate that benzopyran ring opening in Me-SP occurs in both the excited singlet state and the lowest triplet state. Photoisomerization in Me-SP does not lead to an all-trans isomer because of steric hindrance due to the two methyl groups in the 3' position and the one methyl group in the 3 position, but instead leads to a cisoid isomer X characterized by a lifetime of about 3 s at 297 K and an absorption centred at 440 nm. X is formed exclusively from the excited singlet state of Me-SP. Two triplet species, one of which was formed from the other, were detected. Their lifetimes were 25 ns and 2.2 μs respectively at 297 K. The first triplet T was assigned to the lowest triplet state of Me-SP and the second triplet ^3Y to the lowest triplet state of a species (different from X) formed just after Cz.sbnd;O bond rupture. The triplet ^3Y relaxes towards the ground state of Me-SP. The activation energy of the T -〉 ^3Y process is about 5 kcal mol^-^1. |
| topic | V |
| uid | nat_lic_papers_NLZ174721374 |