Excited state dynamics of anthraquinones and electron transfer from ground-state triethylamine to the second and/or lowest excited triplet states of anthraquinones

1992 ◽  
Vol 104 (2) ◽  
Author(s):  
Kumao Hamanoue ◽  
Toshihiro Nakayama
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Ground State ◽  
Triplet States ◽  
Excited Triplet ◽  
Excited State Dynamics ◽  
Excited Triplet States

Monitoring the Formation and Decay of Transient Photosensitized Intermediates Using Pump-Probe UV Resonance Raman Spectroscopy. I: Self-Modeling Curve Resolution

2003 ◽  
Vol 57 (4) ◽  
pp. 439-447 ◽  
Author(s):  
James A. Kleimeyer ◽  
Joel M. Harris
Keyword(s):  
Factor Analysis ◽  
Excited State ◽  
Ground State ◽  
Pure Component ◽  
Triplet States ◽  
Time Resolved ◽  
Pump Probe ◽  
Excited Triplet ◽  
Curve Resolution ◽  
Excited Triplet States

Resolution of transient excited-state Raman scattering from ground-state and solvent bands is a challenging spectroscopic measurement since excited-state spectral features are often of low intensity, overlapping the dominant ground-state and solvent bands. The Raman spectra of these intermediates can be resolved, however, by acquiring time-resolved data and using multidimensional data analysis methods. In the absence of a physical model describing the kinetic behavior of a reaction, resolution of the pure-component spectra from these data can be accomplished using self-modeling curve resolution, a factor analysis technique that relies on the correlation in the data along a changing composition dimension to resolve the component spectra. A two-laser UV pump-probe resonance-enhanced Raman instrument was utilized to monitor the kinetics of amine quenching of excited-triplet states of benzophenone. The formation and decay of transient intermediates were monitored over time, from 15 ns to 100 μs. Factor analysis of the time-resolved spectral data identified three significant components in the data. The time-resolved intensities at each Raman wavenumber shift were projected onto the three significant eigenvectors, and least-squares criteria were developed to find the common plane in the space of the eigenvectors that includes the observed data. Within that plane, the three pure-component spectra were resolved using geometric criteria of convex hull analysis. The resolved spectra were found to arise from benzophenone excited-triplet states, diphenylketyl radicals, and the solvent and ground-state benzophenone.

Protonation of some non-transition metal phthalocyanines — spectral and photophysicochemical consequences

2012 ◽  
Vol 16 (07n08) ◽  
pp. 885-894 ◽  
Author(s):  
Abimbola O. Ogunsipe ◽  
Mopelola A. Idowu ◽  
Taofeek B. Ogunbayo ◽  
Isaac A. Akinbulu
Keyword(s):  
Transition Metal ◽  
Rate Constant ◽  
Rate Equation ◽  
Aluminum Chloride ◽  
Ground State ◽  
Triplet States ◽  
Metal Phthalocyanines ◽  
Excited Triplet ◽  
Kinetics Of ◽  
Excited Triplet States

The photophysics and photochemistry of phthalocyanine complexes of magnesium (MgPc), aluminum chloride (ClAlPc) and zinc (ZnPc) are studied in N,N′-dimethylformamide (DMF). The values obtained for the photophysical and photochemical parameters are normal for simple metallophthalocyanine (MPc) complexes. Protonation of the azomethine bridges reduced the photoactivities of the complexes considerably; however the excited triplet states of the protonated species are more stable towards ground state oxygen. The interaction of the non-protonated MPcs with ground state oxygen is shown to be diffusion-assisted, with bimolecular rate constant values of the order of 1010 M-1.s-1. MgPc could not be protonated; it was easily demetalated by the protonating acid. The kinetics of the demetalation yielded the rate equation: Rate = 0.1[MgPc][H+]2/3

Geometries of the ground and first excited triplet states of thioformaldehyde

1981 ◽  
Vol 59 (22) ◽  
pp. 3200-3203 ◽  
Author(s):  
John D. Goddard
Keyword(s):  
Ground State ◽  
Reasonable Agreement ◽  
Basis Sets ◽  
Triplet States ◽  
Gaussian Basis Sets ◽  
Excited Triplet ◽  
Polarization Functions ◽  
Scf Calculations ◽  
Split Valence ◽  
Excited Triplet States

The geometries of the S0 and T1 states of thioformaldehyde are determined by ab initio SCF calculations with Gaussian basis sets ranging from minimal to double ζ plus both diffuse and polarization functions. The ground state geometries are all in reasonable agreement with experiment but for the n → π* triplet state split valence or double ζ basis sets yield unreasonably long CS bond distances.

Chromophores inspired by the colors of fruit, flowers and wine

2020 ◽  
Vol 92 (2) ◽  
pp. 255-263 ◽  
Author(s):  
Cassio P. Silva ◽  
Gustavo T. M. Silva ◽  
Tássia de Sousa Costa ◽  
Vânia M. T. Carneiro ◽  
Farhan Siddique ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Near Infrared ◽  
Experimental Studies ◽  
Photon Absorption ◽  
Infrared Light ◽  
Triplet States ◽  
State Reduction ◽  
Excited Triplet ◽  
Excited Triplet States

AbstractAnthocyanins, which are responsible for most of the red, blue and purple colors of fruits and flowers, are very efficient at absorbing and dissipating light energy via excited state proton transfer or charge-transfer mediated internal conversion without appreciable excited triplet state formation. During the maturation of red wines, grape anthocyanins are slowly transformed into pyranoanthocyanins, which have a much more chemically stable pyranoflavylium cation chromophore. Development of straightforward synthetic routes to mono- and disubstituted derivatives of the pyranoflavylium cation chromophore has stimulated theoretical and experimental studies that highlight the interesting absorption and emission properties and redox properties of pyranoflavylium cations. Thus, p-methoxyphenyl substitution enhances the fluorescence quantum yield, while a p-dimethylaminophenyl substituent results in fast decay via a twisted intramolecular charge-transfer (TICT) state. Unlike anthocyanins and their synthetic analogs (flavylium cations), a variety of pyranoflavylium cations form readily detectable excited triplet states that sensitize singlet oxygen formation in solution and exhibit appreciable two-photon absorption cross sections for near-infrared light, suggesting a potential for applications in photodynamic therapy. These excited triplet states have microsecond lifetimes in solution and excited state reduction potentials of at least 1.3 V vs. SCE, features that are clearly desirable in a triplet photoredox catalyst.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

Excited state dynamics and electron transfer in a phosphorus(V) porphyrin – TEMPO conjugate

2021 ◽  
Vol 133 (3) ◽  
Author(s):  
PRASHANTH K PODDUTOORI ◽  
NOAH HOLZER ◽  
BRANDON J BAYARD ◽  
YURI E KANDRASHKIN ◽  
GARY LIM ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Excited State Dynamics
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