Kinetics of the Excited Singlet and Triplet States of Vapor‐Phase Phenanthrene

1967 ◽  
Vol 47 (1) ◽  
pp. 95-101 ◽  
Author(s):  
G. L. Powell
Keyword(s):  
Vapor Phase ◽  
Triplet States ◽  
Excited Singlet ◽  
Singlet And Triplet States ◽  
Kinetics Of

Photophysical and Photochemical Properties of Some Fluorescent Derivatives of Vitamin B1

1987 ◽  
Vol 42 (5) ◽  
pp. 485-489 ◽  
Author(s):  
B. Marciniak
Keyword(s):  
Vitamin B1 ◽  
Emission Spectra ◽  
Photochemical Reactions ◽  
Triplet States ◽  
Excited Singlet ◽  
Yield Data ◽  
Singlet And Triplet States ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Fluorescent Derivatives

Absorption and emission spectra, depopulation kinetics of the lowest excited singlet and triplet states and acid-base equilibria of two fluorescent vitamin B, derivatives, the products I and II of the reaction of N-methylated vitamine B, with cytidine and adenosine, respectively, were investigated. Analysis of the lifetime and quantum yield data indicate that at 77 K emissions are the main processes of deactivation of the S1 and T1 states for the free ion and protonated forms. The pKa values indicate a much higher acidity in the excited singlet and triplet states than in the ground state. I and II undergo very slow photochemical reactions in solution in the presence of oxygen (Φ ~ 10-4).

Environmental photodegradation of pyrimidine fungicides — Kinetics of the visible-light-promoted interactions between riboflavin and 2-amino-4-hydroxy-6-methylpyrimidine

2002 ◽  
Vol 80 (1) ◽  
pp. 62-67 ◽  
Author(s):  
E Haggi ◽  
S Bertolotti ◽  
S Miskoski ◽  
F Amat-Guerri ◽  
N A García
Keyword(s):  
Visible Light ◽  
Molecular Oxygen ◽  
Superoxide Anion ◽  
Flash Photolysis ◽  
Triplet States ◽  
Excited Singlet ◽  
Singlet Molecular Oxygen ◽  
Time Resolved ◽  
Singlet And Triplet States ◽  
Kinetics Of

To clarify the evolution of pyrimidine fungicides under natural aquatic environmental conditions, the visible-light-promoted degradation of the model fungicide 2-amino-4-hydroxy-6-methylpyrimidine (AHMPD) has been studied in air-equilibrated pH 6 aqueous solutions in the presence of riboflavin (Rf), employing time-resolved and stationary kinetic–spectroscopic methods. AHMPD, a compound practically inert towards the attack of singlet molecular oxygen (O2(1Δg)), quenches excited singlet and triplet states of Rf with rate constants of 2.7 × 109 M–1 s–1 and 2.7 × 107 M–1 s–1, respectively. In the presence of AHMPD, the photodecomposition of Rf, which occurs from the excited triplet state of the pigment, depends on the concentration of the fungicide: at [Formula: see text]40–50 mM a limited photochemistry occurs due to the quenching of excited singlet Rf, while at ca. 5–10 mM triplet Rf is largely photogenerated and subsequently quenched either by oxygen, giving rise to O2(1Δg), or by AHMPD, yielding semireduced Rf through an electron transfer process. Flash photolysis experiments and indirect auxiliary tests confirm the presence of superoxide anion generated by the reaction of Rf anion radical with the dissolved oxygen. The neat result of this intricate scheme of competitive reactions is the photodegradation of both AHMPD and Rf, mainly through a superoxide anion-mediated oxidation, although some contribution of O2(1Δg)-mediated photooxidations cannot be disregarded.Key words: photooxidation, pyrimidine derivatives, riboflavin, singlet molecular oxygen, superoxide anion.

scholarly journals Organic molecules with inverted gaps between first excited singlet and triplet states and appreciable fluorescence rates

Matter ◽  
2021 ◽  
Author(s):  
Robert Pollice ◽  
Pascal Friederich ◽  
Cyrille Lavigne ◽  
Gabriel dos Passos Gomes ◽  
Alán Aspuru-Guzik
Keyword(s):  
Organic Molecules ◽  
Triplet States ◽  
Excited Singlet ◽  
Singlet And Triplet States

Photochemical reactions of 2,2?-furil. Solvent dependent photoreduction via the lowest excited singlet and triplet states

1992 ◽  
Vol 5 (6) ◽  
pp. 355-360 ◽  
Author(s):  
Hiroyasu Inoue ◽  
Tadamitsu Sakurai ◽  
Toshihiko Hoshi ◽  
Isao Ono ◽  
Jun Okubo
Keyword(s):  
Photochemical Reactions ◽  
Triplet States ◽  
Excited Singlet ◽  
Singlet And Triplet States
Sign in / Sign up

Export Citation Format

Share Document