The interaction between the excited triplet state of ketones and olefins: the role of triplet exciplexes

1979 ◽  
Vol 57 (3) ◽  
pp. 342-347 ◽  
Author(s):  
Rafik O. Loutfy ◽  
S. K. Dogra ◽  
R. W. Yip
Keyword(s):  
Rate Constants ◽  
Binding Energies ◽  
Acetonitrile Solution ◽  
Important Process ◽  
Quenching Rate ◽  
Triplet Energy ◽  
Excited Triplet ◽  
Triplet Exciplexes ◽  
Diffusion Controlled

The quenching of triplet acetone in degassed acetonitrile solution by electron-rich and electron-deficient olefins has been measured by flash emission technique. With the exception of fumaronitrile, the efficiency of quenching of triplet ketones by olefins is not determined by the triplet energy of the ketone, but by the ability of the excited ketone to donate or accept electrons. The results are consistent with the assumption that back dissociation of the triplet exciplex is an important process in the overall reaction and accounts for quenching rate constants which are less than those for diffusion-controlled reactions. Lifetimes and binding energies of the triplet exciplexes have been estimated.

Mechanistic studies of aromatic ketone-sensitized photoreduction of bis(acetylacetonato)copper(II)

1983 ◽  
Vol 61 (5) ◽  
pp. 801-808 ◽  
Author(s):  
Yuan L. Chow ◽  
Gonzalo E. Buono-Core ◽  
Bronislaw Marciniak ◽  
Carol Beddard
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Decay Rates ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Aromatic Ketone ◽  
Quantum Yields ◽  
Triplet States ◽  
Quenching Rate ◽  
Triplet Energy

Bis(acetylacetonato)copper(II), Cu(acac)2, quenches triplet excited states of ketones and polynuclear aromatic hydrocarbons efficiently, but only aromatic ketones with high triplet energy successfully sensitize photoreduction of Cu(acac)2 in alcohols under nitrogen to give derivatives of aeetylacetonatocopper(I), Cu(acac). For the triplet state benzophenone-sensitized photoreduction of Cu(acac)2, the quantum yields of photoreduction (ΦC) and those of benzophenone disappearance (ΦB) were determined in methanol with various concentrations of Cu(acac)2. The values of the quenching rate constant, kq, determined from these two types of monitors on the basis of the proposed mechanism were in good agreement (6.89 ~ 7.35 × 109 M−1 s−1). This value was higher, by a factor of about two, than that obtained from the monitor of the benzophenone triplet decay rates generated by flash photolysis in the presence of Cu(acac)2. The quenching rate constants of various aromatic ketone and hydrocarbon triplet states by Cu(acac)2 were determined by flash photolysis to be in the order of the diffusion rate constant and the quantum yields of these photoreductions were found to be far from unity. Paramagnetic quenching, with contributions of electron exchange and charge transfer, was proposed as a possible quenching mechanism. For a series of aromatic ketone sensitizers with higher triplet energy, this mechanism was used to rationalize the observed high quenching rate constants in contrast to the low quantum yields of photoreduction.

The absolute kinetics for radical addition and electronic energy transfer to [1.1.1]propellane

1998 ◽  
Vol 76 (10) ◽  
pp. 1474-1489 ◽  
Author(s):  
P F McGarry ◽  
J C Scaiano
Keyword(s):  
Free Radicals ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Electronic Energy ◽  
Triplet States ◽  
Quenching Rate ◽  
Electronic Energy Transfer ◽  
Diffusion Controlled

Free radicals react more readily with [1.1.1]propellane, 1, than with styrene. For example Et3Si· reacts with 1 and styrene with rate constants of 6 × 108 M-1 s-1 and 2 × 108 M-1 s-1, respectively. Fluorenone, phenanthrene, triphenylene, benzophenone, and pyrene transfer electronic energy to 1 with rate constants well below the diffusion-controlled limit. For example, triplet benzophenone is quenched by 1 with a bimolecular rate constant of 9.9 × 106 M-1 s-1. A linear dependence of the log of the quenching rate constants, log kq, upon the excited-state energy of the donors is found.Key words: propellane, laser flash photolysis, free radicals, triplet states.

scholarly journals Single Pulse Two-Photon Laser-Assisted Reduction of Benzophenone by Triethylamine to Form Excited Benzophenone Ketyl Radical

1994 ◽  
Vol 15 (1) ◽  
pp. 33-46 ◽  
Author(s):  
J. M. Figuera ◽  
R. Sastre ◽  
A. Costela ◽  
I. Garcia-Moreno ◽  
M. T. Al-Hakakk ◽  
...  
Keyword(s):  
Decay Rate ◽  
Rate Constants ◽  
Single Pulse ◽  
Photon Absorption ◽  
Acetonitrile Solution ◽  
Quenching Rate ◽  
Absorption Mechanism ◽  
Ketyl Radical ◽  
Phosphorescence Quenching ◽  
Two Photon

The pulsed laser photolysis at 308 nm of the benzophenone-triethylamine system in acetonitrile solution has been studied at room temperature. In the absence of triethylamine, phosphorescence emission of triplet benzophenone centred at 460 nm and with a lifetime of τ = 27 ± 1 μs is observed. Addition of triethylamine results in quenching of the benzophenone phosphorescence. Quenching rate constants KQ have been determined from emission intensifies and from experimental decay rate constants. The values KQ = (2.6 ± 0.3) × 109 M-1s-1 and KQ = (4.0 ± 0.5) × 109 M-1s-1, respectively, are obtained. On the addition of triethylamine, benzophenone phosphorescence diminishes and simultaneously a new emission with a fast decay rate and centred at 575 nm develops. This signal has been identified as emission from the excited benzophenone ketyl radical. A single pulse two-photon absorption mechanism responsible of the emission at 575 nm has been identified and a kinetic model based on this mechanism has been developed. The model gives a satisfactory quantitative account of both our experimental results and those reported in the literature (quantum yield of radical formation and behaviour of the system as photoinitiator).

The Triplet State of Ketones in Solution: The Role of the Charge Transfer State in the Quenching of Triplet Acetone by Aromatic Molecules

1973 ◽  
Vol 51 (11) ◽  
pp. 1881-1884 ◽  
Author(s):  
R. O. Loutfy ◽  
R. W. Yip
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Energy Difference ◽  
Charge Transfer State ◽  
Triplet Energy ◽  
Excited Triplet ◽  
Aromatic Molecules ◽  
Triplet Energy Transfer ◽  
Transfer State

The rate constants for quenching of triplet acetone by a series of halobenzenes have been determined by flash emission technique. Quenching was found to be approximately a hundred times faster than that for triplet benzophenone. For both triplet ketones, quenching did not decrease with the increase in triplet energy difference between ketone and quencher (as expected for normal endothermic triplet energy transfer) and did not correlate with the i.p. of all of the quenchers studied. All of the qualitative features of the quenching results can be simply interpreted in terms of enhanced coupling of the locally excited triplet ketone and quencher states as a result of interaction with the charge transfer state.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

scholarly journals A New Piano-Stool Ruthenium(II) P-Cymene-Based Complex: Crystallographic, Hirshfeld Surface, DFT, and Luminescent Studies

Crystals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 13
Author(s):  
Mohd. Muddassir ◽  
Abdullah Alarifi ◽  
Mohd. Afzal
Keyword(s):  
Density Functional ◽  
Weak Interactions ◽  
Energy Levels ◽  
Hirshfeld Surface ◽  
Binding Energies ◽  
Orbital Energy ◽  
Aminosalicylic Acid ◽  
Full Characterization

A new complex (Ru(η6-p-cymene)(5-ASA)Cl2) (1) where 5-ASA is 5-aminosalicylic acid has been prepared by reacting the ruthenium arene precursors ((η6-arene)Ru(μ-Cl)Cl)2, with the 5-ASA ligands in a 1:1 ratio. Full characterization of complex 1 was accomplished by elemental analysis, IR, and TGA following the structure obtained from a single-crystal X-ray pattern. The structural analysis revealed that complex 1 shows a “piano-stool” geometry with Ru-C (2.160(5)- 2.208(5)Å), Ru-N (2.159(4) Å) distances, which is similar to equivalents sister complex. Density functional theory (DFT) was used to calculate the significant molecular orbital energy levels, binding energies, bond angles, bond lengths, and spectral data (FTIR, NMR, and UV–VIS) of complex 1, consistent with the experimental results. The IR and UV–VIS spectra of complex 1 were computed using all of the methods and choose the most appropriate way to discuss. Hirshfeld surface analysis was also executed to understand the role of weak interactions such as H⋯H, C⋯H, C-H⋯π, and vdW interactions, which play a significant role in the crystal environment’s stability. Moreover, the luminescence results at room temperature show that complex 1 gives a more intense emission band positioned at 465 nm upon excitation at 330 nm makes it a suitable candidate for the building of photoluminescent material.

scholarly journals The Role of H2C2O4 and Na2CO3 as Precipitating Agents on The Physichochemical Properties and Photocatalytic Activity of Bismuth Oxide

2020 ◽  
Vol 18 (1) ◽  
pp. 129-137
Author(s):  
Yayuk Astuti ◽  
Rizka Andianingrum ◽  
Abdul Haris ◽  
Adi Darmawan ◽  
Keyword(s):  
Photocatalytic Activity ◽  
Methyl Orange ◽  
Physicochemical Properties ◽  
Bismuth Oxide ◽  
Rate Constants ◽  
Degradation Rate ◽  
Precipitation Method ◽  
Methyl Orange Degradation ◽  
Methyl Orange Dye

AbstractSynthesis of bismuth oxide synthesis through the precipitation method using H2C2O4 and Na2CO3 precipitating agents, identification of physicochemical properties and its photocatalysis activity for methyl orange degradation were conducted. The bismuth oxide synthesis was undertaken by dissolving Bi(NO3)3.5H2O in HNO3, then added precipitating agents to form precipitate. The results showed that bismuth oxide produced by H2C2O4 precipitating agent was a yellow powder containing a mixture of α-Bi2O3 (monoclinic) and β-Bi2O3 (tetragonal), porous with size of 28-85 μm. Meanwhile, the use of Na2CO3 as precipitating agent resulted in bismuth oxide consisting of α-Bi2O3 and β-Bi2O3 and Bi2O4, irregular shape without pore being 40-115 μm in size. Bismuth oxide synthesized with H2C2O4 precipitating agent showed higher photocatalytic activity compared to bismuth oxide synthesized using Na2CO3 on degrading methyl orange dye with degradation rate constants of 2.35x10-5 s-1 for H2C2O4 and 1.81x10-5 s-1 for Na2CO3.

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