摘要:

Successive coupling reactions (catalysed by Cu(I)/Pd(II) systems) between 8-bromo-3,3-diphenyl-[3H]naphtho[2,1-b]pyran, 2-methylbut-3-yn-2-ol and appropriate thiophene- or bithiophene halides afforded mono- or bichromophoric chromenes bearing a thienylethynyl or a bithienylethynyl group. Spectrokinetic study using flash photolysis conditions showed interesting photochromic properties regarding, especially, the “colorability” of the new compounds.

ISSN:1058-725X    

DOI:10.1080/10587250008023827

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Light controlled on- and off-switching of intramolecular energy and charge transfer is demonstrated in donor-switch-acceptor (D-S-A) supermolecules. The supermolecules are designed based on our experience on donor-bridge-acceptor (D-B-A) systems. Switching function is achieved by incorporating optically bistable photochromic fulgides and diarylethenes and proved via fs transient absorption. For both transfer processes, the transfer function is suppressed in the closed form of the switching sub-unit.

ISSN:1058-725X    

DOI:10.1080/10587250008023828

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Structure effect on photochromic mechanism of 1,3,3-trimethylspiro[indoline-2,3′-[3H]naphtho[2,1,-b][1,4]oxazine] (SP1), 1,3-Dimethyl-3,2′-(1,3 -propylene)spiro[indoline-2,3′-[3H] naphtho[2,1-b][1,4]oxazine] (SP2) and 1,2′-(1,3-propylene),3,3-dimethylspiro[indo- line-2,3′ [3H]naphtho[2,1-b][1,4]oxazine](SP3) have been studied by nanosecond laser photolysis. Because of different connective positions of 1,3-propylene group in SP2 and SP3, the photochromic behaviours of them are quite different. One photoproduct of SP2 was only detected, and its lifetime is about 0.15μs. However, two colored forms of SP3 were detected after UV irradiation. The lifetimes of them are much longer than that of C-SP2. The semiempirical computational results by AM1 method were coincided with the experimental results.

ISSN:1058-725X    

DOI:10.1080/10587250008023829

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Photoreversible photochromic systems can be analysed quantitatively even if the photoi-somers have not been isolated. Quantum yields of photocoloration and photodecoloration and UV / visible spectra of each photoisomer can be extracted simultaneously by numerical simulation and fitting of Absλvstime curves recorded under continuous monochromatic irradiation at selected wavelengths.

ISSN:1058-725X    

DOI:10.1080/10587250008023830

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Three isomers of N,N′-dibenzy-biquinolinium dibromide were synthesized and their photoinduced coloration properties were investigated in the thin poly(N-vinylpyrrolidone) films. Upon photo-irradiation, the colorless film of 4,4′-biquinolinium salt became intense purple and had a near IR-absorption at 970 nm, whose color gradually bleached, reaching original ones. While photo-induced absorption maxima of 6,6′-biquinolinium salt does not shift to longer wavelength and 5,5′-one exhibits thermochromism.

ISSN:1058-725X    

DOI:10.1080/10587250008023831

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A variable temperature X-ray crystallographic analysis ofN-(5-chloro-2-hydroxybenzylidene)-4-hydroxyaniline showed the crystal structure change associated with the thermochromism.

ISSN:1058-725X    

DOI:10.1080/10587250008023832

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Cis- andtrans-azobenzenes adsorbed in NaY, Na-mordenite, and Na-ZSM-5 were irradiated using 313- and 254-nm lights. Thecis-transisomer ratio in the photostationary state produced in the zeolites was compared with that in cyclohexane. It was found that Na+in the cavities did not significantly affect the ratio although for stilbene a drastic change in the ratio was caused most likely by electrostatic interaction between the carbon-carbon double bond and Na+. For azobenzene it seems probable on the basis of the results obtained by semiempirical molecular orbital calculation (AM1) that Na+interacts with a lone pair of one of the two nitrogen atoms, but not with the π-orbital of the nitrogen-nitrogen double bond.

ISSN:1058-725X    

DOI:10.1080/10587250008023833

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Photochromism of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (1a) and 1,2-bis(2-methyl-6-nitro-1-benzothiophen-3-yl)perfluorocyclo-pentene (2a) in single-crystalline phases was investigated. Upon irradiation with 366 nm light the colorless crystals of1aand2aturned red and green, respectively. The colored crystals are due to the formation of the closed-ring isomers,1band2b. The colored crystals were bleached by irradiation with visible light. The direction of the electronic transition moment of1bin crystal was estimated from the absorption anisotropy of 535 nm band. When the photogenerated green colored crystal of2awas observed under polarized light, the colored crystal showed dichroism of yellow and blue. The yellow and blue colors were attributed to two perpendicular electronic transitions of2bat 465 and 600 nm, respectively.

ISSN:1058-725X    

DOI:10.1080/10587250008023834

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A study of photochromic dihydroindolizines and diarylethylenes was carried out. The photochromism for these molecules is based on an electrocyclic 6π-process. Photochromic films were prepared by embedding these molecules in polythiourethane matrices and their potential as holographic recording material was evaluated.

ISSN:1058-725X    

DOI:10.1080/10587250008023835

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A novel all-optical parallel switching device was demonstrated by using photoinduced changes of a complex refractive index in a guided mode thin film composed of silver and polymer containing photochromic dyes. An incident angle of a probe beam was set at a value corresponding to the minimum reflection due to the guided mode. Pulsed laser excitation caused changes of absorption of the polymer films due to photochromism, which resulted in the increase of reflection because the guided mode condition was changed. According to the Kramers-Kronig relationship the real part also changes, which results in the shift of the minimum. Appropriate wavelength can be selected for all-optical switching in this geometry. We used photochromic spiropyran dispersed in polystyrene. Self-held parallel switching was achieved upon UV or visible laser excitation with response times less than 20 ns.

ISSN:1058-725X    

DOI:10.1080/10587250008023836

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor