Room-Temperature Reactions of the Intermediate(s) Generated by Flash Photolysis of (η5-C5H5)Fe(CO)2CH3

1998 ◽  
Vol 17 (6) ◽  
pp. 1166-1168 ◽  
Author(s):  
Karen L. McFarlane ◽  
Peter C. Ford
Keyword(s):  
Room Temperature ◽  
Flash Photolysis

LASER FLASH PHOTOLYSIS OF RHODOPSIN AT ROOM TEMPERATURE

1977 ◽  
Vol 26 (6) ◽  
pp. 601-605 ◽  
Author(s):  
R. Bensasson ◽  
E. J. Land ◽  
T. G. Truscott
Keyword(s):  
Room Temperature ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1066-1076
Author(s):  
Hideo Tomioka ◽  
Junichi Nakajima ◽  
Hidehiko Mizuno ◽  
Eiji Iiba ◽  
Katsuyuki Hirai
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Room Temperature ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Benzene Solution ◽  
Laser Flash ◽  
Spin Resonance ◽  
Structure Reactivity Relationship ◽  
Resonance Laser

A series of triplet 9-triptycyl(aryl)carbenes, where aryl groups are phenyl, 1- and 2-naphthyl, and 9-anthryl, is generated by photolysis of the corresponding diazomethanes and observed directly by spectroscopic means. Their structures are characterized by electron spin resonance (ESR) spectroscopy in a 2-methyltetrahydrofuran matrix at 77 K, and the reactivities are investigated by laser flash photolysis in degassed benzene solution at room temperature. Comparison of the data with other arylcarbenes bearing a series of substituents, i.e., hydrogen, phenyl, naphthyl, and anthryl groups, revealed an interesting relationship between structures and reactivities of triplet arylcarbenes.Key words: steric protection, stability of triplet carbenes, electron spin resonance, laser flash photolysis, structure-reactivity relationship.

Singlet Mechanism for Trans → Cis Photoisomerization of Quaternary Salts of 4-Substituted 4′-Azastilbenes (R = CN, H, CH3, and OCH3) and their Quinolinium Analogues. VIII

1985 ◽  
Vol 40 (5) ◽  
pp. 525-537 ◽  
Author(s):  
H. Görner ◽  
A. Fojtik ◽  
J. Wróblewski ◽  
L. J. Currell
Keyword(s):  
Triplet State ◽  
Low Temperatures ◽  
Room Temperature ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Ion Pairs ◽  
Laser Flash ◽  
Quantum Yields ◽  
Polar Solvents ◽  
Effects Of Temperature

The trans → cis photoisomerization of a series of substituted stilbazolium salts (At+X− , At+: trans-1-alkyl-4-[4-R-styryl]-pyridinium and -quinolinium, R = CN. H, CH3 and OCH3, X− = I and ClO4−) was studied by laser flash photolysis and steady state irradiation measurements. The quantum yields of cis ⇄ trans photoisomerization (ϕc → t and ϕt → c ) and of fluorescence of the trans isomers (ϕf) were determined in several solvents at room temperature and at low temperatures in mixtures of either 2-methyltetrahydrofuran-dichloromethane or ethanolmethanol (E-M). In polar solvents at room temperature ϕt → c is substantial ( ≧ 0.3) and ϕf is small (10−3-10−2). Competition of fluorescence and an activated step in the trans → cis pathway is indicated by the effects of temperature on ϕf and ϕt → c (activation energy: 2 - 3 kcal/mol). A transient, observed only at low temperatures (lifetime τT > 0.5 ms in E-M below -170°C), is assigned to the lowest triplet state with trans configuration. On the basis of the effects of temperature on ϕf, ϕt → c , and the triplet yield and those of quenchers on ϕf and ϕt → c , involvement of the triplet state in the twisting process at room temperature is excluded. Therefore, a singlet mechanism is suggested for the trans → cis photoisomerization of the stilbazolium salts examined. Significant reduction of ϕt → c for iodides in solvents of moderate polarity, where ion pairs are present, is accounted for by photoinduced electron transfer in competition to trans → cis photoisomerization.

Studies of triplet chlorophyll by microbeam flash photolysis

1966 ◽  
Vol 295 (1440) ◽  
pp. 1-12 ◽  
Keyword(s):  
Half Life ◽  
Room Temperature ◽  
Flash Photolysis ◽  
Singlet State ◽  
Excited Singlet State ◽  
Intermolecular Distance ◽  
Plant Leaves ◽  
Excited Singlet ◽  
Cationic Detergent ◽  
Photolysis Apparatus

A microbeam flash photolysis apparatus has been developed for use with samples 50 to 250 μ m square, and from 5 to several hundred microns thick. Triplets of chlorophyll a and b were observed in a number of solid solvents, including cholesterol, at room temperature without prior outgassing. In cholesterol the triplet yield decreased with increasing concentration according to the Stern-Volmer law, but the half life of the chlorophyll b triplet was 3 ± 0.2 ms, and independent of concentration. Therefore, the excited singlet state but not the triplet is quenched by a concentration-dependent process. The half-quenching concentration of 2 x 10 -3 M, corresponding to a mean intermolecular distance of 95 Å, points to quenching by inductive resonance. No triplets of chlorophyll appeared on flashing normal or etiolated plant leaves. Leaves treated with cationic detergent gave triplets in a yield of 15%, and exhibited increased fluorescence.

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