Synthesis and Characterization of Novel Platinum Acetylide Oligomers

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.

Photochemical Electron Transfer in the System Polypyrrole-Methylene Blue

1994 ◽  
Vol 47 (6) ◽  
pp. 1163 ◽  
Author(s):  
D Matthews ◽  
A Altus ◽  
A Hope
Keyword(s):  
Methylene Blue ◽  
Electron Transfer ◽  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Vitamin K1 ◽  
Photochemical Reduction ◽  
Long Chain

Methylene Blue incorporated into colloidal oxidized polypyrrole was investigated by absorption spectroscopy and laser flash photolysis. The absorption spectra of Methylene Blue and polypyrrole were unaffected by incorporation. Flash photolysis transients of Methylene Blue and triplet Methylene Blue in ethanol were affected by 1,4-benzoquinone and 1,4-benzoquinol but not by the long-chain naphthoquinone Vitamin K1. Incorporation of Methylene Blue in polypyrrole produced distinct changes in the flash photolysis transients of Methylene Blue and triplet Methylene Blue. Very long-lived transients, with lifetimes of the order of 10 ms, were observed. These effects were accompanied by long-lived changes in the absorption spectrum of Methylene Blue. The transients were modified by the addition of 1,4-benzoquinone but not 1,4-benzoquinol. The results indicate photochemical reduction of oxidized polypyrrole by triplet Methylene Blue with the production of stable long-lived species capable of reducing 1,4-benzoquinone.

Effect of β-bromo substitution on the photophysical properties of meso-phenyl, meso-carbazole, and meso-triphenylamine porphyrins

2012 ◽  
Vol 16 (04) ◽  
pp. 370-379 ◽  
Author(s):  
Joy E. Haley ◽  
Weijie Su ◽  
Kristi M. Singh ◽  
Jennifer L. Monahan ◽  
Jonathan E. Slagle ◽  
...  
Keyword(s):  
Near Infrared ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Photophysical Properties ◽  
Heavy Atom ◽  
Nanosecond Laser ◽  
Free Base ◽  
Structure Property ◽  
Absorption Data ◽  
Absorption And Emission

We present results of an experimental photophysical study of a series of novel brominated and non-brominated porphyrins that contain phenyl, carbazole, or triphenylamine in the meso-position. In addition we have looked at the effects of incorporating a zinc metal into the porphyrin system relative to the free base. Structure-property relationships are established using various absorption and emission techniques including femtosecond pump probe transient absorption and nanosecond laser flash photolysis. With slightly increasing electron donating strength (phenyl < carbazole < triphenylamine) red shifts were observed in all data. The same effect was observed upon the addition of bromine in the beta position. Due to the heavy atom affect of the bromines both the singlet and triplet excited state lifetimes were significantly shorter in the brominated porphyrins. For the T1–Tn absorption data we observe a large absorption in the near infrared region with the brominated carbazole and triphenylamine. The largest effect of the addition of zinc was in the ground state absorption and emission where a blue shift in the data was observed. Some effects were also observed in the kinetic decays with zinc as the metal compared to the free base porphyrins.

Absorption spectroscopy of singlet CH2 near 11 200 cm–1

2001 ◽  
Vol 79 (2-3) ◽  
pp. 347-358 ◽  
Author(s):  
K Kobayashi ◽  
T J Sears
Keyword(s):  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Energy Levels ◽  
Zero Point ◽  
Laser Flash ◽  
Infrared Region ◽  
Transient Absorption Spectroscopy

New spectra of methylene, CH2, in the near infrared region of the singlet band system have been obtained. They were detected by laser transient absorption spectroscopy following excimer laser flash photolysis of ketene, CH2CO, at 308 nm. The new data provide information on the nature and energies of rotational levels in three vibronic states that lie between approximately 11 500 and 13 000 cm–1 above the zero point level of the lower, ã1A1, state. Taken together with previous measurements, a fairly complete picture of the vibronic energy levels of CH2 in this region can be built up. There is generally good agreement with the recent computational studies on the singlet states of CH2, but some evidence for discrepancies for levels with K = 3 and higher near the minimum of the [Formula: see text]1B1 potential surface. PACS No.: 33.20Ea

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

2020 ◽  
Author(s):  
Leandro Scorsin ◽  
Leticia Martins ◽  
Haidi Fiedler ◽  
Faruk Nome ◽  
RENE NOME
Keyword(s):  
Acetic Acid ◽  
Proton Transfer ◽  
Electronic State ◽  
Ground State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Proton Transfer Reaction ◽  
Ground Electronic State ◽  
Experimental Conditions

In the present work, we study the transient laser-induced formation of 4-nitrophenolate (4-NPO<sup>-</sup>) 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<sup>-</sup> 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<sup>-</sup>/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 <i>(GSPT)</i>.

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

2020 ◽  
Author(s):  
Leandro Scorsin ◽  
Leticia Martins ◽  
Haidi Fiedler ◽  
Faruk Nome ◽  
RENE NOME
Keyword(s):  
Acetic Acid ◽  
Proton Transfer ◽  
Electronic State ◽  
Ground State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Proton Transfer Reaction ◽  
Ground Electronic State ◽  
Experimental Conditions

In the present work, we study the transient laser-induced formation of 4-nitrophenolate (4-NPO<sup>-</sup>) 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<sup>-</sup> 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<sup>-</sup>/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 <i>(GSPT)</i>.

Scavenging of photogenerated singlet molecular oxygen and superoxide radical anion by sulpha drugs - Kinetics and mechanism

2004 ◽  
Vol 82 (12) ◽  
pp. 1752-1759 ◽  
Author(s):  
Marta Díaz ◽  
Marta Luiz ◽  
Sonia Bertolotti ◽  
Sandra Miskoski ◽  
Norman A García
Keyword(s):  
Visible Light ◽  
Ground State ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Singlet Molecular Oxygen ◽  
Superoxide Radical Anion ◽  
Sulpha Drugs

The ability of the sulfanilic antibiotics (SDs), dapsone (DAP), sulfisoxazole (SFX), sulfadiazine (SFD), and sulfanilic acid (SFNA) to act as scavengers of the visible-light-photogenerated species superoxide radical anion (O2·–) and singlet molecular oxygen (O2(1Δg)) was studied employing the natural pigment riboflavin (Rf) and the artificial dye Rose Bengal as photosensitisers. A complex mechanism, common to all the SDs studied, was elucidated through stationary photolysis, polarographic detection of oxygen uptake, fluorescence spectroscopy, time-resolved phosphorescence detection of O2(1Δg), and laser flash photolysis. Visible-light irradiation of aqueous and aqueous methanolic solutions of Rf (ca. 0.02 mmol/L) plus SD (ca. 0.5 mmol/L) photogenerated excited singlet and triplet Rf (1Rf* and 3Rf*). Under these experimental conditions, only 3Rf* is quenched either by oxygen, giving rise to O2(1Δg) by electronic energy transfer to dissolved ground-state oxygen, or by SD, yielding semireduced Rf through an electron-transfer process. Complementary experiments performed in pure water employing superoxide dismutase and sodium azide inhibition of oxygen uptake, in parallel with laser flash photolysis data, showed that O2·– is also formed, probably due to the reaction of the anion radical from Rf with dissolved oxygen, yielding also neutral, ground-state Rf. Both active oxygen species, namely, O2·– and O2(1Δg), are quenched by the SDs and, as a result, photodegradation of the SDs — each to a different extent — and photodegradation of the sensitiser itself were observed. The SDs that kinetically behave as the better physical quenchers of O2(1Δg), which are in principle good candidates as photoprotectors, namely, DAP and SFD, suffer photooxidation, exhibiting high to moderate oxygen consumption rates due to the O2·– oxidative pathway, whereas for SFNA and SFX, oxidation predominantly occurs through an O2(1Δg)-mediated mechanism. Microbiological results for SFX, taken as a representative SD, indicate that the photodegradation of the drug, upon visible-light Rf-sensitised irradiation, is accompanied by a net loss in bacteriostatic activity.Key words: photooxidation, singlet oxygen, superoxide radical anion, sulpha drugs.

Synthesis and photodynamics of diphenylethynyl-bridged porphyrin-quinoidal porphyrin hybrids

2015 ◽  
Vol 19 (01-03) ◽  
pp. 219-232 ◽  
Author(s):  
Shuhei Sakatani ◽  
Takuya Kamimura ◽  
Kei Ohkubo ◽  
Shunichi Fukuzumi ◽  
Fumito Tani
Keyword(s):  
Electron Transfer ◽  
Absorption Spectra ◽  
Zinc Complex ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Electrochemical Analysis ◽  
Coupling Reactions ◽  
Free Base ◽  
Electronic Communications

As new donor–acceptor hybrids for energy and/or electron transfer, zinc complex and free-base of a porphyrin-quinoidal porphyrin dyad linked by a diphenylethynyl bridge were prepared via Sonogashira and subsequent Takahashi coupling reactions. The quinoidal porphyrin units have two dicyanomethylene groups at the opposite meso-positions. The UV-vis absorption spectra of the dyads were almost linear summations of the absorption spectra of each component in comparison with those of the monomeric reference compounds, indicating very weak electronic interactions between the chromophores at the ground state. Both zinc complex and free-base of the reference porphyrin exhibited fluorescence in the range of ca. 600–700 nm upon photoexcitation, while the quinoidal porphyrin monomers showed no fluorescence. The considerable quenching (more than 99%) of the porphyrin fluorescence in the dyads suggested significant electronic communications between the subunits of the excited state. The electrochemical analysis confirmed that the first oxidations of the dyads occur at the porphyrin units and the first reductions take place at the quinoidal porphyrin units. Femtosecond laser flash photolysis of the zinc dyad with photoexcitation at 393 nm showed both ultrafast (<1 ps) energy and electron transfer from the porphyrin unit to the quinoidal porphyrin one, which processes resulted in the quenching of the porphyrin fluorescence. On the other hand, the free-base dyad underwent only energy transfer.

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