Excited-state dynamics of naphthoylnaphthvalene: valence isomerization of the lowest excited singlet state and intermolecular hydrogen-atom abstraction of the lowest excited triplet state

1997 ◽  
Vol 266 (5-6) ◽  
pp. 601-606 ◽  
Author(s):  
Toshihiro Nakayama ◽  
Tetsuhiko Nagahara ◽  
Sadao Miki ◽  
Kumao Hamanoue
Keyword(s):  
Excited State ◽  
Hydrogen Atom ◽  
Triplet State ◽  
Singlet State ◽  
Excited Singlet State ◽  
Excited Triplet State ◽  
Hydrogen Atom Abstraction ◽  
Excited Singlet ◽  
Excited Triplet ◽  
Valence Isomerization

Kinetic model for the molecular system of Zinc(II)-2,9,16,23-phthalocyanine tetracarboxylate

2015 ◽  
Vol 24 (01) ◽  
pp. 1550005 ◽  
Author(s):  
Saleh Al-Omari
Keyword(s):  
Kinetic Model ◽  
Triplet State ◽  
Kinetic Parameters ◽  
Ground State ◽  
Singlet State ◽  
Excited Singlet State ◽  
Excited Triplet State ◽  
Initial Population ◽  
Excited Singlet ◽  
Excited Triplet

Using vis absorption, fluorescence spectral experimental data, and time-resolved measurement, we have examined the kinetics of Zinc(II)-2,9,16,23-phthalocyanine tetracarboxylate ( ZnPc ( COONa )4), which is interesting photosensitizer of far red-absorption in water: NaOH solution. The kinetic parameters were measured and/or calculated. The photophysical properties originate principally from the planar macrocycle while the outer substituent and degree of carboxylation seem not to have a considerable influence on the kinetic parameters. The nonradiative rate constants of the first excited state were dominant due to the heavy metal effect. Using the obtained photophysical parameters, the population dynamics were calculated by kinetic model. On nanosecond scale of 15 ns, about 63% population of the first excited-singlet state is retrieved by the ground state. Whereas, the rest of population are deactivated to the first excited-triplet state. Later on, during about 7 μs starting from the initial decay of the first excited singlet state, the first excited singlet state and the first excited triplet state were completely empty, meanwhile the ground state retrieved its initial population. Due to the fact that ZnPc ( COONa )4 has strong absorption, long lifetimes of the first singlet and triplet excited states, and fast intersystem crossing, it may be suitable for nonlinear optical studies.

The photochemistry of ring-substituted cinnamyl acetates

2006 ◽  
Vol 84 (9) ◽  
pp. 1146-1154 ◽  
Author(s):  
S A Fleming ◽  
L Renault ◽  
E C Grundy ◽  
J A Pincock
Keyword(s):  
Triplet State ◽  
Singlet State ◽  
Acetoxy Group ◽  
Excited Singlet State ◽  
Excited Triplet State ◽  
Quantum Yields ◽  
Excited Singlet ◽  
Major Pathway ◽  
Excited Triplet ◽  
Fluorescence Quantum Yields

The photochemistry of the (E)-cinnamyl acetates ((E)-1-aryl-3-propenyl acetates, 8a–8e) with substituents H, 4-CH3O, 3-CH3O, 4-CF3, and 3-CF3, respectively, was examined in both cyclohexane and methanol solvents. Alkene isomerization (E to Z) occurred more efficiently than other reactions and evidence is presented that this process occurs from the excited triplet state. In a slower process, 1,3-migration of the acetoxy group led to the rearranged 3-aryl-3-propenyl acetate isomers (9a–9e) as the major pathway, particularly in cylohexane. In methanol, the isomeric ethers 3-aryl-3-methoxypropene (14) and 1-aryl-3-methoxypropene (15) were formed by reaction of methanol with the photochemically generated cation. The combined yield of 14 and 15 (95% and 5%, respectively) was quantitative for the 4-methoxyphenyl compound (8b). Independent irradiations of the isomers 9a–9c demonstrated that the ethers 14 and 15 were primary photoproducts from 8 and not secondary photoproducts from 9. Fluorescence quantum yields and excited singlet state lifetimes indicated that the reactions, other than the E to Z isomerization, are from the excited singlet state.Key words: cinnamyl acetates, photochemistry, E/Z isomerization, photocleavage, fluorescence.

Hydrogen-Atom Abstraction from the Solvent by the Lowest Excited Triplet State of Chromone Yielding the β-Keto-Type Solvent Adduct(s)

1998 ◽  
Vol 27 (2) ◽  
pp. 145-146 ◽  
Author(s):  
Toshihiro Nakayama ◽  
Yukiyoshi Torii ◽  
Tadashi Shimizu ◽  
Sadao Miki ◽  
Kumao Hamanoue
Keyword(s):  
Hydrogen Atom ◽  
Triplet State ◽  
Excited Triplet State ◽  
Hydrogen Atom Abstraction ◽  
Excited Triplet

Photochemistry of Nitracrine and its Analogues: Acridine Derivatives as Electron Donors

1984 ◽  
Vol 39 (2) ◽  
pp. 195-200 ◽  
Author(s):  
J. Biedrzycki ◽  
J. Błażejowski ◽  
J. Szychliński ◽  
A. Ledòchowski
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Fluorescence Quenching ◽  
Triplet State ◽  
Uv Radiation ◽  
Electron Acceptor ◽  
Singlet State ◽  
Electron Donors ◽  
Excited Singlet State ◽  
Excited Singlet

Studies on the electron transfer in the excited state from electron donors: acridine, 9- aminoacridine and its derivatives, including nitracrine and its isomers, to CCl4 as a suitable electron acceptor, were undertaken. UV radiation (λ= 366 nm), absorbed only by acridine bases, generates CI- ions. The fluorescence quenching measurements indicate that no interaction appears between molecules of acridine bases in the excited singlet state and CCl4 molecule. A scheme of photochemical processes is proposed which assumes that the triplet state of the base molecule is the reactive one.

Photolysis of ketene. I

1968 ◽  
Vol 46 (14) ◽  
pp. 2353-2360 ◽  
Author(s):  
A. N. Strachan ◽  
D. E. Thornton
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Triplet State ◽  
Singlet State ◽  
Inert Gases ◽  
Inert Gas ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Increasing Temperature

Ketene has been photolyzed at 3660 and 3130 Å both alone and in the presence of the inert gases C4F8 and SF6. The quantum yield of carbon monoxide has been determined at both wavelengths as a function of pressure and temperature. At 3660 Å the quantum yield decreases with increasing pressure but increases with increasing temperature. At 3130 Å the quantum yield with ketene alone remains 2.0 at both 37 and 100 °C at pressures up to 250 mm. At higher pressures of ketene or with added inert gas the quantum yield decreases with increasing pressure. The results are interpreted in terms of a mechanism in which intersystem crossing from the excited singlet state to the triplet state occurs at both wavelengths, and collisional deactivation of the excited singlet state by ketene is single stage at 3660 Å but multistage at 3130 Å.

Sign in / Sign up

Export Citation Format

Share Document