Preparation and Characterization of Aqueous Silica-Based Colloidal Composites Containing Immobilized Organometallic Photosensitizers

Serguievski, Petr; Ford, William E.; Rodgers, Michael A. J.

doi:10.1021/la950624w

Cited by 5 publications

(3 citation statements)

References 35 publications

(68 reference statements)

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“…The nanosecond TUV and TIR laser flash photolysis experiments were carried out using a frequency tripled (355 nm) output of a Q-switched Nd:YAG laser as the excitation source. The setup of the laser system and time-resolved UV spectrometer, as well as step-scan Fourier transform infrared (FTIR) setup, were described previously. The femtosecond TUV experiments were conducted using an ultrafast pump−probe instrument based on Ti:Sapphire laser .…”

Section: Methodsmentioning

confidence: 99%

Mechanism of the Cyclopropenone Decarbonylation Reaction. A Density Functional Theory and Transient Spectroscopy Study

Poloukhtine

Popik

2006

J. Phys. Chem. A

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The density functional theory analysis predicts that the thermal decarbonylation of cyclopropenones proceeds by the sequential and regioselective cleavage of both single bonds in a three-membered ring. The initial ring-opening process results in the formation of a reactive zwitterionic intermediate 6, which is separated from the free alkyne and carbon monoxide by a very low energy barrier. Femtosecond pump-probe transient absorption spectroscopy experiments showed that light-induced decarbonylation is also a stepwise process but apparently proceeds on the excited-state surface. The lifetime of the intermediate in the photodecarbonylation reaction is very short and is dependent on substitution and solvent polarity. Thus, bis-p-anisyl-substituted species decays with tau = 0.6 ps, bis-alpha-naphthyl-substituted intermediate has a lifetime of tau = 11 ps, while the bis(2-methoxy-1-naphthyl)-substituted analogue survives for 83 ps in chloroform and for 168 ps in argon-saturated methanol. The loss of carbon monoxide from these intermediates results in the formation of corresponding acetylenes in an electronically ground state. The addition of triplet quenchers does not affect the dynamics or outcome of the reaction.

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Section: Methodsmentioning

confidence: 99%

Mechanism of the Cyclopropenone Decarbonylation Reaction. A Density Functional Theory and Transient Spectroscopy Study

Poloukhtine

Popik

2006

J. Phys. Chem. A

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“…The laser flash photolysis experiments were carried out with use of a frequency tripled (355 nm) output of a Q-switched Nd:YAG laser as the excitation source. The setup of the laser system and time-resolved UV spectrometer was described previously …”

Section: Methodsmentioning

confidence: 99%

Highly Efficient Photochemical Generation of a Triple Bond: Synthesis, Properties, and Photodecarbonylation of Cyclopropenones

Poloukhtine

Popik

2003

J. Org. Chem.

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UV irradiation of alkyl-, aryl-, and heteroatom-substituted cyclopropenones results in the loss of carbon monoxide and the formation of quantitative yields of corresponding alkynes. The quantum yield of the photochemical decarbonylation reaction ranges from 20% to 30% for alkyl-substituted cyclopropenones to above 70% for the diphenyl- and dinaphthylcyclorpopenones. Rapid formation (<5 ns) and then a somewhat slower decay (ca. 40 ns) of an intermediate in this reaction was observed by using laser flash photolysis. The DFT calculations allowed us to identify this intermediate as a zwitterionic species formed by a cleavage of one of the carbon-carbon bonds of the cyclopropenone ring. The latter then rapidly loses carbon monoxide to produce the ultimate acetylenic product. Despite their high photoreactivity, cyclopropenones were found to be thermally stable compounds with the exception of hydroxy- and methoxy-substituted cyclopropenones. The latter undergo rapid solvolysis in hydroxylic solvents even at room temperature. The application of this reaction to the in situ generation of the enediyne structure was illustrated by the photochemical preparation of benzannulated enediyne 12.

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“…Laser flash-photolysis experiments were carried out using a setup at Bowling Green State University based on a Nd:YAG laser with a pulse width of 6−7 ns (Continuum). The detailed arrangement has been described previously …”

Section: Methodsmentioning

confidence: 99%

Electronic Substituent Effects in Quenching of¹O₂by Diaryl Tellurides

Serguievski

Detty

1997

Organometallics

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Singlet-oxygen quenching by a series of substituted diaryl tellurides was investigated in 10% aqueous methanol by monitoring the competitive inhibition of oxidation of 1,3-diphenylisobenzofuran. The extent of quenching of the sensitizer triplet state was determined by repeating the analysis in both air- and O2-saturated solutions and by laser flash-photolysis experiments. A Hammett analysis of the rate of quenching as a function of substituent constant (σ) gave a ρ value of −0.5, which is significantly lower than the ones reported for other chalcogenides. Although this value does not dispute the existence of a charge-transfer intermediate, it suggests that a strong contribution from the heavy-atom effect of Te is present and that Te is relatively insensitive to inductive electronic substituent effects. The efficiency of chemical quenching in the system was estimated to be 2−9% of the overall quenching of 1O2.

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Preparation and Characterization of Aqueous Silica-Based Colloidal Composites Containing Immobilized Organometallic Photosensitizers

Cited by 5 publications

References 35 publications

Mechanism of the Cyclopropenone Decarbonylation Reaction. A Density Functional Theory and Transient Spectroscopy Study

Mechanism of the Cyclopropenone Decarbonylation Reaction. A Density Functional Theory and Transient Spectroscopy Study

Highly Efficient Photochemical Generation of a Triple Bond: Synthesis, Properties, and Photodecarbonylation of Cyclopropenones

Electronic Substituent Effects in Quenching of¹O₂by Diaryl Tellurides

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Preparation and Characterization of Aqueous Silica-Based Colloidal Composites Containing Immobilized Organometallic Photosensitizers

Cited by 5 publications

References 35 publications

Mechanism of the Cyclopropenone Decarbonylation Reaction. A Density Functional Theory and Transient Spectroscopy Study

Mechanism of the Cyclopropenone Decarbonylation Reaction. A Density Functional Theory and Transient Spectroscopy Study

Highly Efficient Photochemical Generation of a Triple Bond: Synthesis, Properties, and Photodecarbonylation of Cyclopropenones

Electronic Substituent Effects in Quenching of1O2by Diaryl Tellurides

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Electronic Substituent Effects in Quenching of¹O₂by Diaryl Tellurides