Reactivity of the (1? g )2 and 1? g states of oxygen produced by direct laser excitation

Abstract

The ('A& and 'Ag states of oxygen have been produced by direct laser (He-Ne and Nd-YAG) excitation of oxygen at high pressure dissolved in a suitable solvent, and their reactivities with various substrates investigated. For 9,lO-dimethylanthracene and 1,3-diphenylisobenzofuran, the quantum yields for ('A& excitation are, within experimental error, twice those for 'Ag excitation. In the reactions of 'Ag oxygen with 9,lO-dimethylanthracene and tetraphenylcyclopentadienone, both chemical reaction (rate kr) and physical quenching (rate kq) are observed. For 9,lO-dimethylanthracene, kq/kr -0.6, and for tetraphenylcyclopentadienone kq/kr -1.7. With 1,3-diphenylisobenzofuran, k,/kr is in the range 0-1. It is shown unambiguously that 'Ag oxygen reacts with two tertiary amines, triethylamine and tropinone, in addition to being quenched. For triethylamine, kqlkr -11.* The other low lying singlet state of oxygen, 'Xi, which is frequently also formed, is apparently very readily quenched to the 'Ag level.' 1661

Direct 1O2 optical excitation: A tool for redox biology

“…Experiments employing this band to excite 1 O 2 started in the 1970s, basically aiming to address several physical chemical parameters like chemical reactions and reaction rates [99], [100], [122], [123], [124], [125], oxygen luminescence [101], [126], [127], [128], or even oxygen lasing in the red and IR [129] (for more recent studies on molecular oxygen lasing schemes see also [130], [131], [132], [133]). In fact, one of the first determinations of 1 O 2 reaction rates with aminoacids was obtained by optically pumping 1 O 2 at 1064 nm in D 2 O, which thereafter reacted with histidine, tryptophan, methionine, tyrosine and alanine (in this order of decreasing reactivity) [134].…”

“…Basically it is the dimol counterpart of the 1270 nm monomol transition (two 1270 nm photons have the same energy as one 633 nm photon), with an energy of 1.96 eV. This transition has been employed to assess physical and/or chemical parameters, mainly in high pressure oxygen although there are studies in organic solvents too [99], [101], [123], [173], [174], [175], [176].…”

Ozonides de phosphite source d'oxygène singulet: rendement, mécanisme

“…Par contre pour la tttraphtnylcyclopentadienone, si la valeur de p est la mCme que celle obtenue par Evans et Tucker (26) la valeur de k, diffkre sensiblement. Cet tcart est probablernent dQ aux incertitudes exptrimentales mais aussi a la nature difftrente du solvant (CC12FCCIF2) et a l'estimation de la durte de vie de I'oxygene singulet dans ce solvant.…”

Determination of physical (kq) and chemical (kr) rate constants for singlet oxygen quenching using the thermolysis of a naphthalenic endoperoxide in H2O and D2O

“…[6][7][8][9][10] In all these processes, the scavenging of 1 O 2 by compounds involves two pathways : physical quenching which occurs through an energy transfer with the rate constant k q and the chemical quenching which results in the formation of oxidation products with the rate constant k r . 11 Overall rate constants (k r + k q ) have been determined for thousands of compounds 12 since they can readily be measured either by continuous or flash photolysis [13][14][15][16][17][18][19][20][21][22] or by using a standardized chemical source of 1 O 2 such as naphthalenic endoperoxides. [23][24][25][26][27][28][29][30] Reported values for the chemical rate constants k r are scarcer 12 since usual methods require the precise measurement of the amount of oxidation products formed when the starting material is submitted to a given amount of 1 O 2 .…”