Time-Resolved Study of Light-Induced Ground State Proton Transfer from Acid Medium to 4-Nitrophenolate

In the present work, we study the transient laser-induced formation of 4-nitrophenolate (4-NPO-) in the ground electronic state and subsequent proton transfer reaction with acetic acid and water with numerical calculations and laser flash photolysis. We employ the Debye-Smoluchowski spherically-symmetric diffusion model of photoacid proton transfer to determine experimental conditions for studying thermally activated chemical reactions in the ground electronic state. Numerically calculated protonation and deprotonation probabilities for 4-NPO- and 4-nitrophenol (4-NPOH) in both ground and excited states showed the feasibility of efficiently producing the ground state anion in the photoacid cycle. We performed laser flash photolysis measurements of 4-NPOH to characterize the photo-initiated ground state protonation and deprotonation rate constants of 4-NPO-/4-NPOH as a function of acetic acid, pH, temperature and viscosity. Overall, the work presented here shows a simple way to study fast competing bimolecular proton transfer reactions in non-equilibrium conditions in the ground electronic state (GSPT).

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Proton Transfer in Anthocyanins and Related Flavylium Salts. Determination of Ground-State Rate Constants with Nanosecond Laser Flash Photolysis

The Journal of Physical Chemistry A ◽

10.1021/jp0140421 ◽

2002 ◽

Vol 106 (7) ◽

pp. 1248-1255 ◽

Cited By ~ 38

Author(s):

Antonio L. Maçanita ◽

Paulo F. Moreira, ◽

João C. Lima ◽

Frank H. Quina ◽

Chang Yihwa ◽

...

Keyword(s):

Proton Transfer ◽

Ground State ◽

Rate Constants ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Laser Flash ◽

Nanosecond Laser ◽

State Rate ◽

Nanosecond Laser Flash Photolysis

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Synthesis and Characterization of Novel Platinum Acetylide Oligomers

MRS Proceedings ◽

10.1557/proc-771-l4.21 ◽

2003 ◽

Vol 771 ◽

Author(s):

Thomas M. Cooper ◽

Benjamin C. Hall ◽

Daniel G. McLean ◽

Joy E. Rogers ◽

Aaron R. Burke ◽

...

Keyword(s):

Absorption Spectra ◽

Ground State ◽

Near Infrared ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Laser Flash ◽

Structure Property ◽

Ground State Absorption ◽

Excitation Spectra ◽

C Nmr

AbstractAs part of an effort to develop a spectroscopic structure-property relationship in platinum acetylide oligomers, we have prepared a series of bidentate Pt(PBu3)2L2 compounds. The ligand was the series o-syd-C6H4-CΞC-(C6H4-CΞC)n-H, n = 0,1,2. The terminal oligomer unit consisted of a sydnone group ortho to the acetylene carbon. The compounds were characterized by various methods, including 13C-NMR, ground state absorption, fluorescence, phosphorescence and laser flash photolysis. The acetylenic 13C-NMR resonances showed sydnone influences that decreased with increasing number of monomer units. The ground state absorption spectra were slightly red shifted from those of the baseline oligomers not having a sydnone group. The low temperature emission and excitation spectra showed complex dependence on excitation and emission wavelengths, suggesting the chromphores resided in a distribution of solvent environments and conformations. Finally, broad triplet state absorption spectra were observed, with absorption throughout the visible and near infrared regions.

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Benzylchlorocarbene: UV Absorption Spectrum, Kinetics for 1,2-H Migration and Mechanism for Reaction With Acetic Acid as Determined by Combined Continuous and Laser-Flash Photolysis

Laser Chemistry ◽

10.1155/1990/62819 ◽

1990 ◽

Vol 10 (5-6) ◽

pp. 267-275 ◽

Cited By ~ 3

Author(s):

R. Bonneau ◽

M. T. H. Liu ◽

R. Subramanian ◽

B. Linkletter ◽

I. D. R. Stevens

Keyword(s):

Absorption Spectrum ◽

Acetic Acid ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Laser Flash ◽

Uv Absorption ◽

Quenching Rate ◽

Continuous Irradiation ◽

Insight Into ◽

Uv Absorption Spectrum

The UV absorption spectrum of benzylchlorocarbene, generated by laser flash photolysis of 3-chloro-3- benzyldiazirine, has been observed in the 290-330 nm range. The lifetime of this species, 18 ns at 25°C, is determined by the rate of the 1,2-H migration to produce chlorostyrenes. Quenching rate constants of this carbene by acetic acid and tetramethylethylene have been measured. Comparison of this kinetic data with the quantitative analysis of the products obtained under continuous irradiation gives further insight into the mechanisms of carbene-acetic acid reactions.

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Direct detection of methylphenylgermylene and 1,2-dimethyl-1,2-diphenyldigermene — Kinetic studies of their reactivities in solution

Canadian Journal of Chemistry ◽

10.1139/v06-107 ◽

2006 ◽

Vol 84 (7) ◽

pp. 934-948 ◽

Cited By ~ 13

Author(s):

William J Leigh ◽

Ileana G Dumbrava ◽

Farahnaz Lollmahomed

Keyword(s):

Acetic Acid ◽

Rate Constants ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Direct Detection ◽

Kinetic Studies ◽

Laser Flash ◽

Absolute Rate ◽

Hydrocarbon Solvents ◽

Diffusion Controlled

Photolysis of 1,3,4-trimethyl-1-phenylgermacyclopent-3-ene (5) in hydrocarbon solvents containing isoprene, methanol, or acetic acid affords 2,3-dimethyl-1,3-butadiene (DMB) and the expected trapping products of methyl phenylgermylene (GeMePh) in chemical yields exceeding 90%. The germylene has been detected in hexane solution by laser flash photolysis as a short-lived species (τ ~ 2 µs) exhibiting a UV-vis absorption spectrum centered at λmax = 490 nm. It decays with second-order kinetics and a rate constant close to the diffusion-controlled limit, with the concomitant growth of a second longer-lived transient (λmax = 420 nm) that is assigned to a mixture of (E)- and (Z)-1,2-dimethyl-1,2-diphenyldigermene (4). Absolute rate constants have been determined for the reactions of the germylene with primary and tertiary amines (n-BuNH2 and Et3N, respectively), acetic acid (AcOH), a terminal alkyne and alkene, isoprene, DMB, CCl4, and the group 14 hydrides Et3SiH and Bu3SnH. GeMePh is slightly more reactive than GePh2 towards all the reagents studied in this work; both are significantly less reactive than GeMe2 toward the same substrates. Absolute rate constants for the reactions of 4 have also been measured or assigned upper limits in every case and are compared to previously reported values for tetraphenyl- and tetramethyl-digermene with the same reagents.Key words: germylene, digermene, kinetics, laser flash photolysis, germirane, germirene, vinylgermirane, complex, UV–vis spectrum, insertion, addition.

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TiO2 Photocatalysis of the Organophosphorus Fenamiphos: Insight into the Degradation Mechanism

ISRN Environmental Chemistry ◽

10.1155/2013/319178 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8

Author(s):

H. Mountacer ◽

S. M. Nemmaoui ◽

S. Rafqah ◽

G. Voyard ◽

M. Sarakha

Keyword(s):

Titanium Dioxide ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Degradation Mechanism ◽

Laser Flash ◽

Order Rate Constant ◽

Excitation Wavelength ◽

Experimental Conditions ◽

Positive Mode ◽

Insight Into

The photocatalytic degradation of the organophosphorus fenamiphos (FN) was studied using titanium dioxide as a photocatalyst and 365 nm as an excitation wavelength. Under our experimental conditions and in aerated solutions, the irradiation in the presence of TiO2 P25 (1.0 g L−1) permitted the evaluation of the half lifetime to 9.5 minutes. Laser flash photolysis experiments showed the formation of an initial species owing to the attack of the hydroxyl radical on FN. It was identified as the adduct OH•-FN. The second order rate constant for its formation was evaluated to 7.3×109 moL−1 L s−1. All the products are formed via the formation of such transient intermediate. They were identified by means of HPLC/MS using electrospray in positive mode (ESI+). Two main processes are responsible for FN photocatalytic transformation: (i) hydroxylation on the aromatic structure and (ii) the scission of the C–O bond. A mechanistic scheme was proposed for the photocatalytic process of FN using titanium dioxide. An efficient mineralization was observed within 24 hours by using a suntest setup.

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Competing photodehydration and excited-state intramolecular proton transfer (ESIPT) in adamantyl derivatives of 2-phenylphenols

Canadian Journal of Chemistry ◽

10.1139/v10-102 ◽

2011 ◽

Vol 89 (2) ◽

pp. 221-234 ◽

Cited By ~ 15

Author(s):

Nikola Basarić ◽

Nikola Cindro ◽

Yunyan Hou ◽

Ivana Žabčić ◽

Kata Mlinarić-Majerski ◽

...

Keyword(s):

Excited State ◽

Carbon Atom ◽

Proton Transfer ◽

Phenyl Ring ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Laser Flash ◽

Intramolecular Proton Transfer ◽

Hydroxyl Group ◽

Quantum Yields

2-Phenylphenol derivatives strategically substituted with a hydroxyadamantyl substituent were synthesized and their photochemical reactivity was investigated. Derivatives 9 and 10 undergo competitive excited-state intramolecular proton transfer (ESIPT) from the phenol to the carbon atom of the adjacent phenyl ring and formal ESPT from the phenol to the hydroxyl group coupled with dehydration. These two processes (both via S1) give rise to two classes of quinone methides (QMs) that revert to starting material or react with nucleophiles, respectively. ESIPT to carbon atoms was studied by performing photolyses in the presence of D2O, whereupon deuterium incorporation to the adjacent phenyl ring was observed ([Formula: see text] = 0.1–0.2). The competing formal ESPT and dehydration takes place with quantum yields that are an order of magnitude lower and was studied by isolation of photomethanolysis products. Derivative 8 did not undergo ESIPT to carbon atom. Owing to the presence of an intramolecular H bond, an efficient ESIPT from the phenol to the hydroxyl group coupled with dehydration gives a QM that efficiently undergoes electrocyclization (overall [Formula: see text] = 0.33), to give chroman 16. In addition, spiro[adamantane-2,9′-(4′-hydroxy)fluorene] (12) undergoes ESIPT, unlike the previously reported unreactive parent 2-hydroxyfluorene. The reactive singlet excited states of the prepared biphenyl and fluorene molecules were characterized by fluorescence spectroscopy, whereas laser flash photolysis (LFP) was performed to characterize the longer lived QM intermediates.

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