Photochemical synthesis, 22. On photochemical cycloaddition: Cyclopentenone

1968 ◽  
Vol 46 (15) ◽  
pp. 2535-2547 ◽  
Author(s):  
P. de Mayo ◽  
J-P. Pete ◽  
M. Tchir
Keyword(s):  
Triplet State ◽  
Quantum Efficiency ◽  
Photochemical Synthesis ◽  
Triplet States ◽  
Mechanistic Studies ◽  
Rapid Reaction

Cyclopentenone has been added photochemically to a wide variety of olefins and the quantum efficiency determined. Mechanistic studies indicate a rapid reaction involving a triplet state by a process which is not stereospecific, but which does not allow complete equilibration. Evidence is provided which suggests that cyclopentenone reacts photochemically from two triplet states, but that only the higher leads to cycloaddition.

Spin-Polarized Molecular Triplet States as Qubits: Phosphorus Hyperfine Coupling in the Triplet State of Benzoisophosphinoline

2020 ◽  
Vol 11 (18) ◽  
pp. 7569-7574
Author(s):  
Joseph A. Christensen ◽  
Jiawang Zhou ◽  
Nikolai A. Tcyrulnikov ◽  
Matthew D. Krzyaniak ◽  
Michael R. Wasielewski
Keyword(s):  
Triplet State ◽  
Hyperfine Coupling ◽  
Triplet States ◽  
Spin Polarized

scholarly journals Triplet State Formation of Chromophoric Dissolved Organic Matter in Atmospheric Aerosols: Characteristics and Implications

2020 ◽  
Author(s):  
Qingcai Chen ◽  
Zhen Mu ◽  
Li Xu ◽  
Mamin Wang ◽  
Jin Wang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Triplet State ◽  
Atmospheric Aerosols ◽  
Formation Rate ◽  
Chromophoric Dissolved Organic Matter ◽  
Biomass Combustion ◽  
Triplet States ◽  
Ambient Aerosols ◽  
Paramagnetic Resonance

Abstract. There is chromophore dissolved organic matter (CDOM) in the atmosphere, which may form triplet-state chromophoric dissolved organic matter (3CDOM*) to further driving the formation of reactive oxygen species (ROS) under solar illumination. 3CDOM* contributes significantly to aerosol photochemistry and plays an important role in aerosol aging. We quantify the ability to form 3CDOM* and drive the formation of ROS by primary, secondary and ambient aerosols. Biomass combustion has the strongest 3CDOM* generation capacity and the weakest vehicle emission capacity. Ambient aerosol has a stronger ability to generate 3CDOM* in winter than in summer. Most of the triplet states generation conform to first-order reaction, but some of them do not due to the different quenching mechanism. The structural-activity relationship between the CDOM type and the 3CDOM* formation capacity shows that the two types of CDOM identified, which similar to the nitrogen-containing chromophores contributed 88 % to the formation of 3CDOM*. The estimated formation rate of 3CDOM* can reach ~ 100 μmol m−3 h−1 in the atmosphere in Xi'an, China, which is approximately one hundred thousand-times the hydroxyl radical (•OH) production. This study verified that 3CDOM* drives at least 30 % of the singlet oxygen (1O2) and 31 % of the •OH formed by aerosols using the spin trapping and electron paramagnetic resonance technique.

Photochemical Synthesis of s-Triazolo[3,4-b]benzothiazole and Mechanistic Studies on Benzothiazole Formation

1997 ◽  
Vol 62 (17) ◽  
pp. 5766-5770 ◽  
Author(s):  
G. Jayanthi ◽  
S. Muthusamy ◽  
R. Paramasivam ◽  
V. T. Ramakrishnan ◽  
N. K. Ramasamy ◽  
...  
Keyword(s):  
Photochemical Synthesis ◽  
Mechanistic Studies

scholarly journals Electron Nuclear Double Resonance of the Chlorophyll Triplet State in the Water-Soluble Chlorophyll Protein from Brassica oleracea: Investigation of the Effect of the Binding Site on the Hyperfine Couplings

2020 ◽  
Vol 51 (9-10) ◽  
pp. 925-937
Author(s):  
Alessandro Agostini ◽  
Daniel M. Palm ◽  
Harald Paulsen ◽  
Marilena Di Valentin ◽  
Donatella Carbonera
Keyword(s):  
Triplet State ◽  
Brassica Oleracea ◽  
Double Resonance ◽  
Water Soluble ◽  
Triplet States ◽  
Triplet Energy ◽  
Electron Nuclear Double Resonance ◽  
Light Harvesting Complexes ◽  
Chlorophyll Protein ◽  
Hyperfine Couplings

Abstract An investigation of the photoexcited triplet state of chlorophyll (Chl) a in the water-soluble chlorophyll protein (WSCP) of Brassica oleracea has been carried out by means of electron-nuclear double resonance (ENDOR), achieving a complete assignment of the observed hyperfine couplings corresponding to methine protons and methyl groups of Chl a triplet state. The triplet-state properties, and in particular the hyperfine couplings, were found to be similar to those previously reported for Chl a in the WSCP of Lepidium virginicum. Therefore, the porphyrin ring deformation observed in Brassica oleracea WSCP seems to only slightly affect the spin density of 3Chl a. This may be relevant when considering the robustness of triplet–triplet energy transfer mechanisms, relying on wavefunction overlap, in systems, such as the photosynthetic light-harvesting complexes, in which Chl triplet states with distorted geometries are involved.

Optische Spin-Polarisation im Triplett-Zustand von Naphthalin

1969 ◽  
Vol 24 (6) ◽  
pp. 952-967 ◽  
Author(s):  
M. Schwöhrer ◽  
H. Slxl
Keyword(s):  
Triplet State ◽  
Spin Polarization ◽  
Rate Constants ◽  
Uv Light ◽  
Lattice Relaxation ◽  
Stimulated Emission ◽  
Spin Lattice Relaxation ◽  
Spin Component ◽  
Triplet States ◽  
Selection Rules

Naphthalene, which is excited into the lowest triplet state by unpolarized UV-Iight shows a strong deviation from the Boltzman distribution within the three magnetic sublevels, which is ob­served by ESR. We call this deviation optical spin polarization. In the mixed crystal C10D8: 0.2% C10H8 , where the undeuterated Naphthalene acts as trap at 4.2 °K, the optical spin polarization exceeds the thermal spin polarization such that a steady state inversion between two of the mag­netic sublevels appears. This results in an emissive ESR-transition (stimulated emission of micro- waves). The time dependence of the spin polarization after switching on or off the UV-light is described by a superposition of two exponential functions with different rate constants. - The optical spin polarization is due to spin selection rules for the intersystem crossing process (ISC). These involve primarily the molecular symmetry. - The experimental results of the present paper are these selection rules for the pumping processes: The metastable triplet state is populated via the spin component τx.The depopulation rate constants of the three spin components τx, τv and τz are kx = 0.65 sec-1, ky=0.4 sec-1 and kz=O.15 sec-1 .The spin lattice relaxation probabilities are of the order of 1 sec-1. The latter are dependent on the direction of the magnetic field and on the concentration of the populated triplet states. - These results are compared with a theory of ISC.

Triplet state quantum yields for some arom atic hydrocarbons and xanthene dyes in dilute solution

1967 ◽  
Vol 299 (1458) ◽  
pp. 348-353 ◽  
Keyword(s):  
Triplet State ◽  
State Formation ◽  
Heavy Atom ◽  
Quantum Yields ◽  
Triplet States ◽  
Dilute Solution ◽  
Perturbation Techniques ◽  
Excited Singlet ◽  
Xanthene Dyes ◽  
Extinction Coefficients

Quantum yields of triplet state formation and extinction coefficients of the triplet states have been determined by direct depletion methods for solutions of anthracene, phenanthrene, 1,2,5,6-dibenzanthracene, fluorescein, dibromofluorescein, eosin and erythrosin. The values obtained for the hydrocarbons are in reasonable agreement with those obtained by other workers using energy transfer and heavy atom perturbation techniques. In all cases which we have studied, the sum of the quantum yields of fluorescence and triplet state formation is equal to unity within the limits of experimental error, showing that radiationless transfer from the excited singlet to the ground state is negligible.

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