The photochemistry of phenanthrene-substituted molecules

1983 ◽  
Vol 61 (5) ◽  
pp. 866-872 ◽  
Author(s):  
Howard E. Zimmerman ◽  
Guo-Sheng Wu
Keyword(s):  
Quantum Yields ◽  
Intersystem Crossing ◽  
Primary Reaction ◽  
Direct Irradiation ◽  
Primary Reaction Product

The photochemistry of 3-methyl-3-(9-phenanthryl)-1-butene was examined as part of an investigation into the effects of having two π chromophores of widely different energies participating in a di-π-methane rearrangement. We observed both direct and sensitized reactivity with quantum yields [Formula: see text] and [Formula: see text]. The primary reaction product from both direct and sensitized photolyses was 1,1-dimethyl-2-(9-phenanthryl)cyclopropane. However, in practice this product was obtained only from sensitized irradiations where it was almost completely unreactive. The triplet reactivity is unusual in that the typical free rotor decay exhibited by triplets does not lead to inhibition of di-π-methane reactivity in this case. This point is discussed. The intersystem crossing efficiency of the phenanthryl vinyl methane reactant was obtained from the sensitization of biacetyl phosphorescence by the phenanthrene derivative at varying biacetyl concentrations. This was [Formula: see text]. This result and the bracketing relationships signify that essentially all of the direct irradiation rearrangement utilizes T1. In addition, from these experiments, 3kd(tot), was determined as 5.8 × 103 s−1. Similarly,3kr = 250 s−1 which is the slowest di-π-methane rearrangement encountered thus far. The rearrangement of the cyclopropane product to form 2-methyl-4-(9-phenanthryl)-1-butene was also investigated. [Formula: see text] was determined to be 0.091 and [Formula: see text] was determined as 0.00072. Thus the interesting contrast was encountered in which the di-π-methane rearrangement proceeds from the triplet while the rearrangement of the cyclopropane product proceeds most efficiently from the singlet.

Cytochrome P450-mediated oxidation of pentafluorophenol to tetrafluorobenzoquinone as the primary reaction product

1993 ◽  
Vol 6 (5) ◽  
pp. 674-680 ◽  
Author(s):  
Cathaline den Besten ◽  
Peter J. van Bladeren ◽  
Erwin Duizer ◽  
Jacques Vervoort ◽  
Ivonne M. C. M. Rietjens
Keyword(s):  
Cytochrome P450 ◽  
Primary Reaction ◽  
Mediated Oxidation ◽  
Primary Reaction Product

The Photolysis in Acidic Aqueous Solutions of the Monooxalato-bisethylenediamine Chromium(III) Cation and the Bisoxalatomonoethylenediamine Chromate(III) Anion: Photolysis Modes and Quantum Yields

1971 ◽  
Vol 49 (3) ◽  
pp. 375-383 ◽  
Author(s):  
A. D. Kirk ◽  
K. C. Moss ◽  
J. G. Valentin
Keyword(s):  
Quantum Yield ◽  
Aqueous Solutions ◽  
Quantum Yields ◽  
Ligand Field ◽  
Intersystem Crossing ◽  
Empirical Correlations ◽  
Complex Ions ◽  
Ethylenediamine Complex ◽  
Ethylenediamine Ligand ◽  
Ph Range

The photolysis reactions of the complex ions [Cr(en)2ox]+ and [Cren(ox)2]− have been studied in the pH range 1 → 3 and at temperatures from 0 to 25 °C. It has been found that both ions photoaquate to a monodentate protonated ethylenediamine complex which then undergoes further aquation thermally with loss of the ethylenediamine ligand. Quantum yields for these aquations were measured for irradiation into the ligand field bands, the values obtained being 0.18 and 0.02, respectively. The results are discussed in terms of known empirical correlations for Cr(III) complexes. Assuming these reactions may occur from the 4T2g state as precursor, arguments are presented that the correlation between quantum yield and ΔE may depend on mixing of the 4T2g and 2Eg states, and its effect on the intersystem crossing rate constant.

Luminescence of 5-Phenyltetrazole and its Derivatives. Part II. Phosphorescence

1984 ◽  
Vol 39 (6) ◽  
pp. 556-559 ◽  
Author(s):  
I. Gryczyński ◽  
A. Kawski ◽  
Z. Grzonka ◽  
A. Rażyńska
Keyword(s):  
Triplet State ◽  
Quantum Yields ◽  
Intersystem Crossing ◽  
Thermal Deactivation ◽  
Fluorescence Quantum Yields ◽  
Radiative Transitions ◽  
Polyvinyl Alcohol Film ◽  
Methyl Derivatives ◽  
Temperature Responses ◽  
Phosphorescence Spectra

The phosphorescence spectra, mean lifetimes of phosphorescence and ratios of phosphorescence/ fluorescence quantum yields have been measured for 5-phenyltetrazole and its three methyl derivatives in a polyvinyl alcohol film over the temperature range of (77-250) K. Temperature responses of the non-radiative intersystem crossing constant. KST, and the non-radiative triplet state deactivation constant, km, have been investigated on the basis of these measurements. The energy of activation for the non-radiative transitions has been determined. With the methyl 5-phenyltetrazoles, the thermal deactivation of the triplet state, contrary to the intersystem crossing, has been found to be influenced by the position of the methyl substituent in the phenyl ring.

Synthesis of sodalite from Brazilian kaolin wastes

Clay Minerals ◽  
2015 ◽  
Vol 50 (5) ◽  
pp. 663-675 ◽  
Author(s):  
Ana Áurea B. Maia ◽  
Roberto F. Neves ◽  
Rômulo S. Angélica ◽  
Herbert Pöllmann
Keyword(s):  
Clay Mineral ◽  
Bayer Process ◽  
Primary Reaction ◽  
Structural Order ◽  
Complete Reaction ◽  
Low Degree ◽  
Source Materials ◽  
Primary Reaction Product

AbstractKaolin wastes from the Capim and Jari regions (Brazil) were used to produce sodalite under the same conditions used in the Bayer process, in order to control its formation when necessary. Of the two kaolin source materials, the kaolinite from the Jari region was more reactive in the synthesis of sodalite, which is attributed to the low degree of structural order of this clay mineral which increased its reactivity. At a temperature of 150°C and with a Na/Al ratio of 2, although the kaolinite did not react completely, sodalitewas the primary reaction product. An increase in the temperature to 200°C provoked the complete reaction of the kaolinite only for the products in which carbonate and sulfate were used. With a Na/Al ratio >2 and for both of the temperatures, the kaolinite reacted completely to form sodalite.

Photochemistry of cyclododecanone

1976 ◽  
Vol 29 (11) ◽  
pp. 2477 ◽  
Author(s):  
PJ Burchill ◽  
AG Kelso ◽  
AJ Power
Keyword(s):  
Cleavage Product ◽  
Quantum Yields ◽  
Intersystem Crossing ◽  
Quantitative Measurements ◽  
Acyclic Ketones ◽  
Triplet Lifetime

Quantitative measurements of the photolytic reactions of cyclododecanone gave quantum yields of reaction and of intersystem crossing as 0.56 and 0.88 respectively, and a triplet lifetime of 1.7 x 10-7 s. Cyclobutanol formation accounts for most of the reaction with only a low yield of the Norrish II cleavage product; this contrasts markedly with the opposite behaviour of acyclic ketones of similar size. The results may be explained by the apparent restriction of rotation in cyclododecanone molecules.

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