One electron oxidation potential as a predictor of rate constants of N-containing compounds with carbonate radical and triplet excited state organic matter

2014 ◽  
Vol 16 (4) ◽  
pp. 832-838 ◽  
Author(s):  
William A. Arnold
Keyword(s):  
Organic Matter ◽  
Excited State ◽  
Rate Constants ◽  
Oxidation Potential ◽  
Triplet Excited State ◽  
Carbonate Radical

Temperature effects on xanthone–β-cyclodextrin binding dynamics

2011 ◽  
Vol 89 (3) ◽  
pp. 395-401 ◽  
Author(s):  
Tamara C. S. Pace ◽  
Cornelia Bohne
Keyword(s):  
Excited State ◽  
Complex Formation ◽  
Ground State ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Equilibrium Constants ◽  
Dissociation Rate ◽  
Activation Entropy ◽  
Triplet Excited State ◽  
Dissociation Rate Constants

The complexation dynamics of the triplet excited state of xanthone with β-cyclodextrin were studied at various temperatures between 10 and 50 °C. Association and dissociation rate constants were determined using the laser flash photolysis quenching methodology with Cu2+ as a quencher. The rate constants for the association and dissociation of triplet xanthone with β-cyclodextrin increased with temperature, while the equilibrium constant for the triplet excited state remained relatively constant. Equilibrium constants for the ground-state complexation of xanthone with β-cyclodextrin were determined from fluorescence studies at various temperatures. The ground-state binding efficiency decreased with temperature and was markedly greater than that of the triplet excited state at all temperatures. The enthalpy and entropy for the β-cyclodextrin complex formation of the ground and triplet excited states fall on the enthalpy–entropy compensation relationship previously established for cyclodextrin complexes. The activation enthalpies for the association and dissociation rate constants for triplet xanthone are similar. The activation entropy is favorable for the association process, whereas a negative activation entropy was measured for the dissociation process, suggesting that solvation plays a key role in the complex formation between xanthone and β-cyclodextrin.

Roles of singlet oxygen and triplet excited state of dissolved organic matter formed by different organic matters in bacteriophage MS2 inactivation

2013 ◽  
Vol 47 (14) ◽  
pp. 4869-4879 ◽  
Author(s):  
Sahid L. Rosado-Lausell ◽  
Hanting Wang ◽  
Leonardo Gutiérrez ◽  
Ofelia C. Romero-Maraccini ◽  
Xi-Zhi Niu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Excited State ◽  
Dissolved Organic Matter ◽  
Singlet Oxygen ◽  
Triplet Excited State ◽  
Organic Matters ◽  
Bacteriophage Ms2

scholarly journals Aqueous reactions of organic triplet excited states with atmospheric alkenes

2019 ◽  
Vol 19 (7) ◽  
pp. 5021-5032 ◽  
Author(s):  
Richie Kaur ◽  
Brandi M. Hudson ◽  
Joseph Draper ◽  
Dean J. Tantillo ◽  
Cort Anastasio
Keyword(s):  
Organic Matter ◽  
Double Bond ◽  
Excited States ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Oxidation Potential ◽  
Water Soluble ◽  
Oxidation Products ◽  
Bond Dissociation ◽  
Triplet Excited States

Abstract. Triplet excited states of organic matter are formed when colored organic matter (i.e., brown carbon) absorbs light. While these “triplets” can be important photooxidants in atmospheric drops and particles (e.g., they rapidly oxidize phenols), very little is known about their reactivity toward many classes of organic compounds in the atmosphere. Here we measure the bimolecular rate constants of the triplet excited state of benzophenone (3BP∗), a model species, with 17 water-soluble C3–C6 alkenes that have either been found in the atmosphere or are reasonable surrogates for identified species. Measured rate constants (kALK+3BP∗) vary by a factor of 30 and are in the range of (0.24–7.5) ×109 M−1 s−1. Biogenic alkenes found in the atmosphere – e.g., cis-3-hexen-1-ol, cis-3-hexenyl acetate, and methyl jasmonate – react rapidly, with rate constants above 1×109 M−1 s−1. Rate constants depend on alkene characteristics such as the location of the double bond, stereochemistry, and alkyl substitution on the double bond. There is a reasonable correlation between kALK+3BP∗ and the calculated one-electron oxidation potential (OP) of the alkenes (R2=0.58); in contrast, rate constants are not correlated with bond dissociation enthalpies, bond dissociation free energies, or computed energy barriers for hydrogen abstraction. Using the OP relationship, we estimate aqueous rate constants for a number of unsaturated isoprene and limonene oxidation products with 3BP∗: values are in the range of (0.080–1.7) ×109 M−1 s−1, with generally faster values for limonene products. Rate constants with less reactive triplets, which are probably more environmentally relevant, are likely roughly 25 times slower. Using our predicted rate constants, along with values for other reactions from the literature, we conclude that triplets are probably minor oxidants for isoprene- and limonene-related compounds in cloudy or foggy atmospheres, except in cases in which the triplets are very reactive.

scholarly journals Phototransformation of pesticides in prairie potholes: effect of dissolved organic matter in triplet-induced oxidation

2016 ◽  
Vol 18 (2) ◽  
pp. 237-245 ◽  
Author(s):  
M. Ekrem Karpuzcu ◽  
Andrew J. McCabe ◽  
William A. Arnold
Keyword(s):  
Organic Matter ◽  
Excited State ◽  
Dissolved Organic Matter ◽  
Prairie Potholes ◽  
Triplet Excited State

Despite the fact that triplet excited state dissolved organic matter (DOM) enhances phototransformation of pesticides by acting as a photosensitizer, it may also decrease the overall phototransformation rate through various mechanisms.

scholarly journals Ultra long‐lived triplet excited state in water at room temperature: Insights on the molecular design of tridecafullerenes

2021 ◽  
Author(s):  
Javier Ramos-Soriano ◽  
Alfonso Pérez-Sánchez ◽  
Sergio Ramírez-Barroso ◽  
Beatriz M. Illescas ◽  
Khalid Azmani ◽  
...  
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Molecular Design ◽  
Triplet Excited State

scholarly journals Triplet energies and excimer formation in meta - and para -linked carbazolebiphenyl matrix materials

2015 ◽  
Vol 373 (2044) ◽  
pp. 20140446 ◽  
Author(s):  
Sergey A. Bagnich ◽  
Alexander Rudnick ◽  
Pamela Schroegel ◽  
Peter Strohriegl ◽  
Anna Köhler
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Spectroscopic Investigation ◽  
Triplet Excited State ◽  
Conjugation Length ◽  
Triplet Energy ◽  
Excimer Formation

We present a spectroscopic investigation on the effect of changing the position where carbazole is attached to biphenyl in carbazolebiphenyl (CBP) on the triplet state energies and the propensity to excimer formation. For this, two CBP derivatives have been prepared with the carbazole moieties attached at the ( para ) 4- and 4 ′ -positions ( p CBP) and at the ( meta ) 3- and 3 ′ -positions ( m CBP) of the biphenyls. These compounds are compared to analogous m CDBP and p CDBP, i.e. two highly twisted carbazoledimethylbiphenyls, which have a high triplet energy at about 3.0 eV and tend to form triplet excimers in a neat film. This torsion in the structure is associated with localization of the excited state onto the carbazole moieties. We find that in m CBP and p CBP, excimer formation is prevented by localization of the triplet excited state onto the central moiety. As conjugation can continue from the central biphenyls into the nitrogen of the carbazole in the para -connected p CBP, emission involves mainly the benzidine. By contrast, the meta -linkage in m CBP limits conjugation to the central biphenyl. The associated shorter conjugation length is the reason for the higher triplet energy of 2.8 eV in m CBP compared with the 2.65 eV in p CBP.

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