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Matthew S. Platz - One of the best experts on this subject based on the ideXlab platform.
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Photochemistry of Tetrasulfur Tetranitride: Laser Flash Photolysis and Quantum Chemical Study.
ChemInform, 2012Co-Authors: Elena A. Pritchina, Matthew S. Platz, Daria S Terpilovskaya, Yuri P Tsentalovich, Nina P. GritsanAbstract:The photochemistry of S4N4 with a highly symmetric cage structure is studied by Laser Flash Photolysis and B3LYP quantum chemical computations.
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A Significant Barrier to 1,2 Hydrogen Migration in Singlet 1‐ Phenylethylidene. A Laser Flash Photolysis Study
ChemInform, 2010Co-Authors: Michelle H. Sugiyama, Sol Celebi, Matthew S. PlatzAbstract:Laser Flash Photolysis of 1-phenyldiazoethane in heptane releases 1-phenylethylidene which can be intercepted with pyridine to form an ylide (λmax=475nm).
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A study of 2-azido-3,5-dichlorobiphenyl by nano- and picosecond Laser Flash Photolysis and computational methods.
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2005Co-Authors: Nina P. Gritsan, Dmitrii A Polshakov, Meng Lin Tsao, Matthew S. PlatzAbstract:The dynamics of singlet 3,5-dichloro-2-biphenylnitrene and the products of its rearrangement were monitored by pico- and nanosecond Laser Flash Photolysis and the results were consistent with the predictions of DFT and ab initio molecular orbital calculations.
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Laser Flash Photolysis Study of Carboethoxynitrene
Organic letters, 2003Co-Authors: Christophe Buron, Matthew S. PlatzAbstract:Laser Flash Photolysis (LFP, 266 nm) of carboethoxyazide produces a mixture of the ethoxycarbonyl radical (λmax = 333 nm, τ = 0.4 μs, CF2ClCFCl2, ambient temperature) and triplet carboethoxynitrene (λmax = 400 nm, τ = 1.5 μs, CF2ClCFCl2, ambient temperature). The carbon-centered radical is selectively scavenged by oxygen allowing sole observation of the triplet nitrene. We deduce that the singlet nitrene has a lifetime between 2 and 10 ns in CF2ClCFCl2 at ambient temperature.
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Laser Flash Photolysis Study of Chlorofluorocarbene
The Journal of Physical Chemistry A, 2003Co-Authors: Eric Michael Tippmann, Matthew S. PlatzAbstract:10-exo-Fluoro-10‘-endo-chlorotricylco[4.3.1.01,6]decadiene-2,4 (1) was synthesized. Continuous Photolysis of 1 (300 nm) generates chlorofluorocarbene 2, which can be intercepted with tetramethylethylene (TME) to form the expected cyclopropane 3. Laser Flash Photolysis (LFP) of 1 (308 nm) in cyclohexane at ambient temperature does not result in the direct detection of 2 by time-resolved UV−vis spectroscopy. However, LFP of 1 in the presence of pyridine produces the intense transient absorption of ylide 4 at 450 nm. The absolute rate constant of reaction of 2 with pyridine is 8.0 × 109 M-1 s-1 in cyclohexane. LFP (266 nm) of 1 in heptane at ambient temperature produces a transient species with a C−F vibration at 1142 cm-1 and a lifetime of 2.5 μs at ambient temperature. The carrier of the transient absorption is assigned to carbene 2 on the basis of density functional theory (DFT) calculations and on the basis of its kinetic behavior. The absolute rate constant of reaction of carbene 2 with TME was determin...
Juan C. Scaiano - One of the best experts on this subject based on the ideXlab platform.
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Laser Flash Photolysis Studies on 4‐Oxocyclohexa‐2,5‐dienylidenes.
ChemInform, 2010Co-Authors: Bradley R. Arnold, Juan C. Scaiano, Götz Bucher, Wolfram SanderAbstract:Reactions of 4-oxocyclohexa-2,5-dienylidene (1) and two derivatives have been investigated using Laser Flash Photolysis techniques. Photolysis of 4-diazocyclohexa-2,5-dien-1-one (4) in 1,1,2-trichlorotrifluoroethane allows the indirect detection of the corresponding carbene 1. The carbene reacts with triplet oxygen at close to the diffusion-controlled rate, forming the carbonyl O-oxide (λ max =470 nm). Reaction of triplet 1 with moderate concentrations of cyclohexane leads to formation of phenoxyl radical (λ max =395 nm)
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Laser Flash Photolysis with nanoliter samples: photonic crystal fibers as ultrasmall smart test tubes
Journal of Materials Chemistry, 2008Co-Authors: Altaf Khetani, Marie Laferrière, Hanan Anis, Juan C. ScaianoAbstract:Photonic crystal fibers play a dual function as a sample container as well as a photonic device supporting mode structure, and in doing so offer new opportunities for carrying out Laser Flash Photolysis experiments with ultrasmall samples. Monitoring light can be transmitted in the fiber by total internal reflection or by the photonic bandgap guiding effect, depending upon the relative refractive index of the fiber material (usually silica) and the liquid filling the holes. Both offer opportunities for transient monitoring in time scales as short as tens of nanoseconds, with enhanced signals with respect to conventional (large sample) Laser Flash Photolysis work.
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Diffuse Reflectance Laser Flash Photolysis Study of Titanium-Containing Zeolites
Chemistry of Materials, 2004Co-Authors: Pedro Atienzar, Avelino Corma, Hermenegildo García, Juan C. ScaianoAbstract:A series of porous titanosilicates (Ti-preferrierite, Ti-ferrierite, Ti/ITQ-6, Ti/ITQ-2, and silylated Ti/MCM-41), all of them active as alkene epoxidation catalysts, have been submitted to diffuse reflectance Laser Flash Photolysis. The transient spectra in the microsecond time domain exhibit characteristic absorption bands at 350 nm (sharp) and 450−800 nm (featureless) attributable to triplet ligand-to-metal charge-transfer state and ejected electrons, respectively. It is proposed that the relative intensity of these two bands is a reflection of the presence of isolated, tetrahedral Ti atoms versus Ti aggregates, the former being considered the most active titanium sites in olefin epoxidation. Our study shows the applicability of Laser Flash Photolysis to the characterization of titanium atoms in titanosilicates.
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Laser Flash Photolysis Study of Jacobsen Catalyst and Related Manganese(III) Salen Complexes. Relevance to Catalysis
Journal of the American Chemical Society, 2001Co-Authors: María J. Sabater, Mercedes Alvaro, Hermenegildo García, Emilio Palomares, Juan C. ScaianoAbstract:The Laser Flash Photolysis and emission properties of a set of five-coordinate manganese(III) Schiff-base complexes have been examined. In contrast to the intramolecular electron transfer between Mn3+ and the equatorial salen ligand reported to occur in the absence of axial coordination, our Laser Flash Photolysis study has shown that the reactivity of the respective excited states is appreciably influenced by the electron donor strength of the apical ligand at the metal center. In fact, homolytic and heterolytic photocleavage of the metal-ligand apical bond can be the most important processes upon Laser excitation, their relative contribution being influenced by medium effects and the sigma-charge donation of the axial ligand. On the other hand, the detection of reactive intermediates such as the oxomanganese(V) salen complex (lambda(max) 530 nm) by Laser Flash Photolysis opens the way to apply this fast detection technique to the study of reaction mechanisms in catalysis by metallic complexes. As a matter of fact, quenching of oxomanganese(V) salen by simple alkenes has been observed by Laser Flash.
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Laser Flash Photolysis of Diphenylsulfonyldiazomethane: Detection of the Sulfene and a Sulfene−Pyridine Ylide
Organic letters, 2000Co-Authors: F. Ortica, Gerd Pohlers, Chris Coenjarts, E. Bejan, J. F. Cameron, Anthony Zampini, M Haigh, Juan C. ScaianoAbstract:The photochemistry of diphenylsulfonyldiazomethane (DSD) was studied by means of nanosecond Laser Flash Photolysis. The photochemical behavior of this molecule upon UV irradiation is characterized by sulfene formation, presumed to arise via Wolff rearrangement of a carbene. We were able to detect the sulfene and the sulfene ylide formed upon sulfene trapping by pyridine. Sulfene quenching by nucleophiles was also examined.
Mamoru Fujitsuka - One of the best experts on this subject based on the ideXlab platform.
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Reaction dynamics of excited radical ions revealed by femtosecond Laser Flash Photolysis
Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2018Co-Authors: Mamoru Fujitsuka, Tetsuro MajimaAbstract:Abstract Herein, we review studies on the dynamics of excited radical ions. The enhanced reactivities of excited radical ions are recognized by many researchers based on product analysis studies conducted around 1980. For cases involving fluorescent excited radical ions, lifetime measurements provide information on excited states, and they sometimes lead to confusion owing to emissive byproducts resulting from their higher reactivities. Nanosecond Laser Flash Photolysis studies provide evidence of the reactions of excited radical ions, and analyses of their kinetics reveal properties such as their excited-state lifetimes despite an indirect manner. Recent femtosecond Laser Flash Photolysis studies provide detailed pictures of excited radical ions, though such studies are few. Furthermore, studies on dyad or triad systems, including excited radical ions, show electron transfer dynamics and disclose characteristics of excited radical ions that differ from those in neutral states. Larger electronic coupling and smaller dumping factor are reported as important characteristics of electron transfer systems of excited radical ions. These systematic studies on excited radical ions demonstrate their suitability for applications.
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Photodissociation of Naphthalene Dimer Radical Cation during the Two-Color Two-Laser Flash Photolysis and Pulse Radiolysis−Laser Flash Photolysis
The journal of physical chemistry. A, 2006Co-Authors: Xichen Cai, Sachiko Tojo, Mamoru Fujitsuka, Tetsuro MajimaAbstract:Photodissociation of naphthalene (Np) dimer radical cation (Np 2 .+ ) to give naphthalene radical cation (Np .+ ) and Np and the subsequent regeneration of Np 2 .+ by the dimerization of Np .+ and Np were directly observed during the two-color two-Laser Flash Photolysis in solution at room temperature. When Np 2 .+ was excited at the charge-resonance (CR) band with the 1064-nm Laser, the bleaching and recovery of the transient absorption at 570 and 1000 nm, assigned to the local excitation (LE) and CR bands of Np 2 .+ , respectively, were observed together with the growth and decay of the transient absorption at 685 nm, assigned to Np .+ . The dissociation of Np 2 .+ proceeds via a one-photon process within the 5-ns Laser Flash to give Np .+ and Np in the quantum yield of 3.2 x 10 -3 and in the chemical yield of 100%. The recovery time profiles of Np 2 .+ at 570 and 1000 nm were equivalent to the decay time profile of Np .+ at 685 nm, suggesting that the dimerization of Np .+ and Np occurs to regenerate Np 2 .+ in 100% yield. Similar experimental results of the photodissociation and regeneration of Np 2 .+ were observed during the pulse radiolysis-Laser Flash Photolysis of Np in 1,2-dichloroethane. The photodissociation mechanism can be explained based on the crossing between two potential surfaces of the excited-state Np 2 .+ and ground-state Np .+ .
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Photochemical Generation of Radical Cations of Dithienothiophenes, Condensed Thiophene Trimers, Studied by Laser Flash Photolysis
The Journal of Physical Chemistry A, 1997Co-Authors: Mamoru Fujitsuka, Tadatake Sato, Takeo Shimidzu, And Akira Watanabe, Osamu ItoAbstract:Photoinduced electron-transfer reactions between dithienothiophene (DTT) and the electron acceptors, p-dinitrobenzene (DNB) and CCl4, have been investigated using nanosecond Laser Flash Photolysis ...
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Laser Flash Photolysis Study of Photophysical and Photochemical Properties of a Higher Fullerene, C76
The Journal of Physical Chemistry A, 1997Co-Authors: Mamoru Fujitsuka, Osamu Ito, Akira Watanabe, Kazunori Yamamoto, Hideyuki FunasakaAbstract:Photophysical and photochemical properties of C76 have been investigated by using nano- and picosecond Laser Flash Photolysis methods. In the nanosecond Laser Flash Photolysis of C76, transient absorption ascribable to the triplet excited state of C76 (TC76*) was observed in the visible and near-IR regions. From the generation of the absorption band of TC76*, the lifetime of the singlet excited state was estimated to be 1.7 ns. Under the presence of β-carotene in toluene, TC76* was deactivated by energy transfer to β-carotene at a 2.6 × 109 M-1 s-1 rate constant. Electron-transfer reaction to TC76* was also confirmed in a benzonitrile solution containing C76 and tetramethyl-p-phenylenediamine (TMPD) as an electron donor. A bimolecular rate constant for quenching of TC76* by TMPD was estimated to be 7.8 × 108 M-1 s-1.
Tetsuro Majima - One of the best experts on this subject based on the ideXlab platform.
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Reaction dynamics of excited radical ions revealed by femtosecond Laser Flash Photolysis
Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2018Co-Authors: Mamoru Fujitsuka, Tetsuro MajimaAbstract:Abstract Herein, we review studies on the dynamics of excited radical ions. The enhanced reactivities of excited radical ions are recognized by many researchers based on product analysis studies conducted around 1980. For cases involving fluorescent excited radical ions, lifetime measurements provide information on excited states, and they sometimes lead to confusion owing to emissive byproducts resulting from their higher reactivities. Nanosecond Laser Flash Photolysis studies provide evidence of the reactions of excited radical ions, and analyses of their kinetics reveal properties such as their excited-state lifetimes despite an indirect manner. Recent femtosecond Laser Flash Photolysis studies provide detailed pictures of excited radical ions, though such studies are few. Furthermore, studies on dyad or triad systems, including excited radical ions, show electron transfer dynamics and disclose characteristics of excited radical ions that differ from those in neutral states. Larger electronic coupling and smaller dumping factor are reported as important characteristics of electron transfer systems of excited radical ions. These systematic studies on excited radical ions demonstrate their suitability for applications.
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Photodissociation of Naphthalene Dimer Radical Cation during the Two-Color Two-Laser Flash Photolysis and Pulse Radiolysis−Laser Flash Photolysis
The journal of physical chemistry. A, 2006Co-Authors: Xichen Cai, Sachiko Tojo, Mamoru Fujitsuka, Tetsuro MajimaAbstract:Photodissociation of naphthalene (Np) dimer radical cation (Np 2 .+ ) to give naphthalene radical cation (Np .+ ) and Np and the subsequent regeneration of Np 2 .+ by the dimerization of Np .+ and Np were directly observed during the two-color two-Laser Flash Photolysis in solution at room temperature. When Np 2 .+ was excited at the charge-resonance (CR) band with the 1064-nm Laser, the bleaching and recovery of the transient absorption at 570 and 1000 nm, assigned to the local excitation (LE) and CR bands of Np 2 .+ , respectively, were observed together with the growth and decay of the transient absorption at 685 nm, assigned to Np .+ . The dissociation of Np 2 .+ proceeds via a one-photon process within the 5-ns Laser Flash to give Np .+ and Np in the quantum yield of 3.2 x 10 -3 and in the chemical yield of 100%. The recovery time profiles of Np 2 .+ at 570 and 1000 nm were equivalent to the decay time profile of Np .+ at 685 nm, suggesting that the dimerization of Np .+ and Np occurs to regenerate Np 2 .+ in 100% yield. Similar experimental results of the photodissociation and regeneration of Np 2 .+ were observed during the pulse radiolysis-Laser Flash Photolysis of Np in 1,2-dichloroethane. The photodissociation mechanism can be explained based on the crossing between two potential surfaces of the excited-state Np 2 .+ and ground-state Np .+ .
Grażyna Stochel - One of the best experts on this subject based on the ideXlab platform.
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New trends in the application of Laser Flash Photolysis – case studies
Journal of Coordination Chemistry, 2010Co-Authors: Łukasz Orzeł, Małgorzata Brindell, Agnieszka Jańczyk, G. Stopa, Grażyna StochelAbstract:Laser Flash Photolysis (LFP) is a powerful tool for spectroscopic and kinetic determination of both primary photophysical transformations and rapid chemical reactions. This method is very useful in...
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Application of high pressure Laser Flash Photolysis in studies on selected hemoprotein reactions.
Biochimica et biophysica acta, 2008Co-Authors: Małgorzata Brindell, Iwona Stawoska, Łukasz Orzeł, Przemysław Łabuz, Grażyna Stochel, Rudi Van EldikAbstract:This article focuses on the application of high pressure Laser Flash Photolysis for studies on selected hemoprotein reactions with the objective to establish details of the underlying reaction mechanisms. In this context, particular attention is given to the reactions of small molecules such as dioxygen, carbon monoxide, and nitric oxide with selected hemoproteins (hemoglobin, myoglobin, neuroglobin and cytochrome P450cam), as well as to photo-induced electron transfer reactions occurring in hemoproteins (particularly in various types of cytochromes). Mechanistic conclusions based on the interpretation of the obtained activation volumes are discussed in this account.
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Laser Flash Photolysis as tool in the elucidation of the nitric oxide binding mechanism to metallobiomolecules
Coordination Chemistry Reviews, 2002Co-Authors: Alicja Wanat, Małgorzata Brindell, Łukasz Orzeł, Rudi Van Eldik, Maria Wolak, Grażyna StochelAbstract:The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolecules. The main emphasis falls on the application of ambient and high pressure Laser Flash Photolysis techniques in the elucidation of the mechanism of the reaction of NO with metals in active centres of biomolecules and complexes of potential medicinal application.
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Laser Flash Photolysis as tool in the elucidation of the nitric oxide binding mechanism to metallobiomolecules
Coordination Chemistry Reviews, 2002Co-Authors: Alicja Wanat, Małgorzata Brindell, Łukasz Orzeł, Rudi Van Eldik, Maria Wolak, Grażyna StochelAbstract:The article presents a sampling of mechanistic studies on nitric oxide binding to metallobiomolecules. The main emphasis falls on the application of ambient and high pressure Laser Flash Photolysis techniques in the elucidation of the mechanism of the reaction of NO with metals in acti v e centres of biomolecules and complexes of potential medicinal application. # 2002 Else v ier Science B.V. All rights reserved
