Photophysical Properties of Conformationally Distorted Metal-Free Porphyrins. Investigation into the Deactivation Mechanisms of the Lowest Excited Singlet State

1994 ◽  
Vol 116 (16) ◽  
pp. 7363-7368 ◽  
Author(s):  
Steve Gentemann ◽  
Craig J. Medforth ◽  
Timothy P. Forsyth ◽  
Daniel J. Nurco ◽  
Kevin M. Smith ◽  
...  
Keyword(s):  
Singlet State ◽  
Photophysical Properties ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Metal Free

Revisiting the photophysical properties and excited singlet-state dipole moments of several coumarin derivatives

2011 ◽  
Vol 79 (3) ◽  
pp. 428-436 ◽  
Author(s):  
Lamine Cisse ◽  
Abdoulaye Djande ◽  
Martine Capo-Chichi ◽  
François Delatre ◽  
Adama Saba ◽  
...  
Keyword(s):  
Singlet State ◽  
Dipole Moments ◽  
Photophysical Properties ◽  
Excited Singlet State ◽  
Coumarin Derivatives ◽  
Excited Singlet

The structure, photochemical reactivity, and photophysical properties of adamantyl X-substituted aryl ethers and a comparison with the alkyl groups, methyl, tert-butyl, and allyl

2005 ◽  
Vol 83 (9) ◽  
pp. 1237-1252 ◽  
Author(s):  
A L Pincock ◽  
J A Pincock
Keyword(s):  
Excited State ◽  
Rate Constants ◽  
Singlet State ◽  
Bond Cleavage ◽  
Photophysical Properties ◽  
Excited Singlet State ◽  
Quantum Yields ◽  
Aryl Ether ◽  
Excited Singlet ◽  
Aryl Ethers

The structure, photophysical properties, and photochemistry of the adamantyl aryl ethers 1 in both methanol and cyclohexane have been examined. UV absorption spectra, 13C NMR chemical shifts, X-ray structures, and Gaussian calculations (B3LYP/6-31G(d)) indicate that these ethers adopt a 90° conformer in the ground state. In contrast, fluorescence spectra, excited singlet state lifetimes, and calculations (TDDFT) indicated a 0° conformer is preferred in the first excited singlet state S1. Irradiation in either solvent results in the formation of adamantane and the corresponding phenol as the major products, both derived from radical intermediates generated by homolytic cleavage of the ether bond. The 4-cyano substituted ether 1j was the only one to form the ion-derived product, 1-methoxyadamantane (16% yield), on irradiation in methanol. Rate constants of bond cleavage for these ethers from S1 were estimated by two different methods by comparison with the unreactive anisoles 2, but the effect of substituents was too small to determine structure–reactivity correlations. The temperature dependence of the quantum yields of the fluorescence of the unsub stituted, 4-methoxy and 4-cyano derivatives of 1 and 2 were also determined. These results indicated that the activated process for 1 was mainly bond cleavage for the 4-cyano substrate whereas for 2, it was internal conversion and intersystem crossing. Key words: aryl ether photochemistry, fluorescence, excited-state rate constants, excited-state temperature effects.

Control of the Photophysical Properties of Polyatomic Molecules by Substitution and Solvation:  The Second Excited Singlet State of Azulene

1999 ◽  
Vol 103 (15) ◽  
pp. 2524-2531 ◽  
Author(s):  
Nicolas Tétreault ◽  
Rajeev S. Muthyala ◽  
Robert S. H. Liu ◽  
Ronald P. Steer
Keyword(s):  
Singlet State ◽  
Photophysical Properties ◽  
Polyatomic Molecules ◽  
Excited Singlet State ◽  
Excited Singlet

Photophysical Properties of Intramolecular Charge-Transfer Excited Singlet State of Aminofluorenone Derivatives

1998 ◽  
Vol 102 (18) ◽  
pp. 3018-3024 ◽  
Author(s):  
Tomoyuki Yatsuhashi ◽  
Yuka Nakajima ◽  
Tetsuya Shimada ◽  
Haruo Inoue
Keyword(s):  
Charge Transfer ◽  
Singlet State ◽  
Intramolecular Charge Transfer ◽  
Photophysical Properties ◽  
Excited Singlet State ◽  
Excited Singlet

Steric effects in the phototransposition reactions of dialkylbenzenes

2006 ◽  
Vol 84 (1) ◽  
pp. 10-20 ◽  
Author(s):  
C M Gonzalez ◽  
J A Pincock
Keyword(s):  
Singlet State ◽  
Activation Barrier ◽  
Photophysical Properties ◽  
Dominant Mode ◽  
Excited Singlet State ◽  
Quantum Yields ◽  
Reactive Intermediate ◽  
Temperature Dependent ◽  
Excited Singlet ◽  
General Observation

The photochemistry, photophysical properties, and temperature dependence (–25 to +65 °C) of fluorescence by quantum yields and excited singlet state lifetimes in acetonitrile have been examined for three sets of dialkylbenzene derivatives: Set 1 — ortho-xylene (10), tetralin (11), and indan (12); Set 2 — 2,3-dimethylbenzonitrile (9-23), 5-cyanotetralin (T-23), and 4-cyanoindan (I-23); and Set 3 — 3,4-dimethylbenzonitrile (9-34), 6-cyanotetralin (T-34), and 5-cyanoindan (I-34). Phototransposition reactions occur for 10, 9-23, 9-34, and T-34. Fitting of the temperature-dependent fluorescence data to an Arrhenius expression gave A and Ea values for all substrates studied except I-23 and I-34. The fluorescence intensity of these two compounds was essentially independent of temperature. For the other compounds, the data revealed that the activation barrier separating the excited singlet state (S1) from the reactive intermediate, a prefulvene biradical, was the important one in determining the reaction efficiency. The dominant mode of decay of the reactive intermediate was internal return to the starting material. Moreover, the general observation was made that nitrile substitution ortho to one of the alkyl groups in these dialkylbenzene derivatives reduced the rate at which they were converted to the reactive intermediate and, therefore, also the efficiency of the phototransposition reactions.Key words: phototranspositions, substituted benzenes, temperature-dependent fluorescence, activation parameters.

The Gold Porphyrin First Excited Singlet State¶

2002 ◽  
Vol 76 (1) ◽  
pp. 47 ◽  
Author(s):  
Joakim Andréasson ◽  
Gerdenis Kodis ◽  
Su Lin ◽  
Ana L. Moore ◽  
Thomas A. Moore ◽  
...  
Keyword(s):  
Singlet State ◽  
Excited Singlet State ◽  
Excited Singlet

Interaction of the Excited Singlet State of Neutral Red with Aromatic Amines

2000 ◽  
Vol 71 (3) ◽  
pp. 300 ◽  
Author(s):  
M. K. Singh ◽  
H. Pal ◽  
A. V. Sapre
Keyword(s):  
Aromatic Amines ◽  
Singlet State ◽  
Neutral Red ◽  
Excited Singlet State ◽  
Excited Singlet
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