Quantum yield for intersystem crossing in nonfluorescent metal porphyrins

1973 ◽  
Vol 18 (4) ◽  
pp. 543-545 ◽  
Author(s):  
K. N. Solov'ev ◽  
M. P. Tsvirko ◽  
V. V. Sapunov
Keyword(s):  
Quantum Yield ◽  
Intersystem Crossing ◽  
Metal Porphyrins

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.

Effects of Pressure and Temperature on the Fluorescence Quantum Yield of N-Methylacridone in Solution Interpreted in Terms of the Eyring Transition-StateTheory

1981 ◽  
Vol 36 (5) ◽  
pp. 489-493
Author(s):  
H.-D. Brauer ◽  
R. Schmidt ◽  
B. Hammerich
Keyword(s):  
Quantum Yield ◽  
Fluorescence Quantum Yield ◽  
Energy Gap ◽  
State Theory ◽  
Intersystem Crossing ◽  
Thermally Activated ◽  
Elevated Pressures ◽  
Condon Factors ◽  
Positive Volume ◽  
Franck Condon

Abstract The influence of temperatur and pressure on the fluorescence quantum yield of N-methylacridone (9,10-dihydro-9-oxo-10-methyl-acridine) in toluene in the range of 283-313 K and 1 bar to 2.5 kbar, respectively, has been investigated. Treatment of the data in terms of the Eyring transition-state theory leads to a consistent interpretation of the observed effect. The unusually large increase of the quantum yield with increasing pressure is attributed to a positive volume of activation, ⊿V≠, for the thermally activated S1-T2 intersystem crossing which is known to be the only deactivation process (of the Si-state) competing with fluorescence. Comparison of the values for ⊿H≠, the activation enthalpy of this process, determined at various pressures, indicates a decrease in ⊿H≠ at elevated pressures. Since ⊿H≠ can be associated with the S1-T2 energy gap involved in intersystem crossing, this result further confirms the conclusion that the change in Franck-Condon factors alone cannot account for the decrease in the intersystem crossing rate with increasing pressure.

Identification of a receiver triplet state in the ultrafast intersystem crossing of carbonylpyrenes

2020 ◽  
Vol 22 (11) ◽  
pp. 6145-6153
Author(s):  
Lekshmi R. S. ◽  
Gayathri B. Kurup ◽  
Sivaranjana Reddy Vennapusa
Keyword(s):  
Quantum Yield ◽  
Triplet State ◽  
Intersystem Crossing

The intersystem crossing receiver triplet state lifetime dictates the efficiency of the triplet quantum yield in carbonylpyrenes.

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.

The mechanism of the photochemical cycloaddition reaction of N-benzoylindole with cyclopentene

1990 ◽  
Vol 68 (10) ◽  
pp. 1685-1692 ◽  
Author(s):  
Bimsara W. Disanayaka ◽  
Alan C. Weedon
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Ground State ◽  
Mechanistic Model ◽  
Cycloaddition Reaction ◽  
Intersystem Crossing ◽  
Triplet Excited State ◽  
Excited State Lifetime ◽  
Yield Data ◽  
Counting Procedure

The mechanism of the photochemical cycloaddition reaction between N-benzoylindole, 1, and cyclopentene to give cyclobutane adducts 2 and 3 has been examined. The triplet excited state lifetime and quantum yield of intersystem crossing were determined for 1 as (2.8 ± 0.3) × 10−8 s and 0.39 ± 0.01, respectively, using the triplet counting procedure. In addition, the dependence of the quantum yield of cycloadduct formation upon the concentration of cyclopentene and upon the concentration of excited state quenchers has been determined. The results are used to propose a mechanistic model in which the triplet excited state of 1 reacts with cyclopentene to give a triplet 1,4-biradical intermediate. Following spin inversion the biradical intermediate reverts to the ground state starting materials or proceeds to the products 2 and 3; this partitioning, along with the quantum yield of intersystem crossing, gives rise to a limiting quantum yield of cycloaddition at infinite alkene concentration of 0.061. It is calculated that 84% of the biradical intermediates revert to the starting materials and 16% proceed to cycloadducts. The quantum yield data are also used to calculate two independent values of the rate constant for reaction of the triplet excited 1 with alkene; the values are (1.8 ± 0.1) × 107M−1 s−1 and (4.0 ± 0.8) × 106 M−1 s−1'. Some evidence for self quenching of the triplet excited state of 1 by ground state 1 was also observed. The quantum yield of intersystem crossing and the triplet excited state lifetime of 1 were found to vary with the solvent used; this is discussed in terms of the possible existence of a charge transfer triplet excited state. Keywords: indole, photocycloaddition, mechanism.

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