Singlet Excited-State Behavior of Uracil and Thymine in Aqueous Solution:  A Combined Experimental and Computational Study of 11 Uracil Derivatives

2006 ◽  
Vol 128 (2) ◽  
pp. 607-619 ◽  
Author(s):  
Thomas Gustavsson ◽  
Ákos Bányász ◽  
Elodie Lazzarotto ◽  
Dimitra Markovitsi ◽  
Giovanni Scalmani ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Excited State ◽  
Computational Study ◽  
Singlet Excited State ◽  
State Behavior ◽  
Uracil Derivatives

The effect of dimerization on the excited state behavior of methylated xanthine derivatives: a computational study

2013 ◽  
Vol 12 (8) ◽  
pp. 1496 ◽  
Author(s):  
Dana Nachtigallová ◽  
Adelia J. A. Aquino ◽  
Shawn Horn ◽  
Hans Lischka
Keyword(s):  
Excited State ◽  
Computational Study ◽  
State Behavior ◽  
Xanthine Derivatives

scholarly journals Excited States of Gold(I) Compounds, Luminescence and Gold-Gold Bonding

1994 ◽  
Vol 1 (5-6) ◽  
pp. 459-466 ◽  
Author(s):  
John P. Fackler ◽  
Zerihun Assefa ◽  
Jennifer M. Forward ◽  
Richard J. Staples
Keyword(s):  
Aqueous Solution ◽  
Excited State ◽  
Triplet State ◽  
Excited States ◽  
Ground State ◽  
Superoxide Anion ◽  
Direct Interaction ◽  
Water Soluble ◽  
State Behavior ◽  
Β Carotene

It has long been established by Khan that the superoxide anion, O2-, generates singlet oxygen, O21Δg, during dismutation. Auranofin, gold-phosphine thiols, β-Carotene, and metal-sulfur compounds can rapidly quench singlet O2. The quenching of the O21Δg, which exists at 7752 cm-1 above the ground state triplet, may be due to the direct interaction of the singlet O2 with gold(I) or may require special ligands such as those containing sulfur coordinated to the metal. Thus we have been examining the excited state behavior of gold(I) species and the mechanisms for luminescence. Luminescence is observed under various conditions, with visible emission ranging from blue to red depending on the ligands coordinated to gold(I). Triplet state emission can be found from mononuclear three coordinate Au(I) species, including species which display this behavior in aqueous solution. A description is given of the luminescent three coordinate TPA (triazaphosphaadamantane) and TPPTS (triphenylphosphine-trisulfonate) complexes, the first examples of water soluble luminescent species of gold(I).

scholarly journals Singlet Excited-State Dynamics of 5-Fluorocytosine and Cytosine:  An Experimental and Computational Study

2005 ◽  
Vol 109 (20) ◽  
pp. 4431-4436 ◽  
Author(s):  
Lluís Blancafort ◽  
Boiko Cohen ◽  
Patrick M. Hare ◽  
Bern Kohler ◽  
Michael A. Robb
Keyword(s):  
Excited State ◽  
Computational Study ◽  
Singlet Excited State ◽  
Excited State Dynamics

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

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