Photoperoxidation of unsaturated organic molecules. 16. Excitation energy fission

Abstract

Is the intensity of the high overtones you see caused by the electrical anharmonicity of the bonds being stretched? B. R. Henry. We have actually looked on the problem more from the point of view of mechanical anharmonicity than of electrical anharmonicity, but in this region of the spectrum it may be impossible to disentangle one from the other. The detailed intensity problem in normal mode language is one that I think we haven't solved, and to my knowledge, neither has anyone else. S. J. STRICKLER. I do not believe you can say the results are all due to electrical anharmonicity. The local mode states are just those for which the mechanical anharmonicity is a maximum. One can think of anharmonicity in terms of a sort of Morse potential-the lower the dissociation energy, the greater the anharmonicity. For a CH2 group, for example, the Morse curve for a symmetric CH stretch would level

Photosensitized Generation of Singlet Oxygen

“…Thus, Brauer and Wagner first demonstrated that both the TI state and 02('Ag) may be formed in the fluorescence quenching by 0, and that the maximum value of Qa can be 2 (72). This important result was confirmed by both authors in the investigation of the self-sensitized photooxygenation of heterocoerdianthrone (73), by Stevens and Ors in their re-evaluation of previous rubrene photooxygenation data (74), and by Wu and Trozzolo (75). Brauer et al (76) and Usui et al (77) determined by the same technique for a larger number of aromatic compounds 1 5 f: + S A 5 2.…”

“…The condition Δ E ST < E Δ = 94 kJ mol −1 is imperative but not sufficient for efficiencies f S Δ = 1. This was first noted by Stevens and Ors, whose re‐evaluation of previous Q po data led to values of f S Δ + S Δ = 1.0 and 1.2 for 9,10‐dimethyl‐1,2‐benzanthracene and tetracene in BNZ, respectively (74). For both compounds, Δ E ST < 94 kJ mol −1 holds true; however, upper excited triplet states T n lie below S 1 in both cases.…”

SENSITIZED PHOTOOXIDATION OF PINENES BY 9,10‐DICYANOANTHRACENE

“…PAP 40:5-11 58 1 converted to singlet oxygen according to an unusual process (Santamaria, 1981). In addition, the singlet state of highly fluorescent molecules has been shown to produce singlet oxygen directly (Wu and Trozzolo, 1979;Stevens and Ors, 1976;Streichen and Foote, 1981). Thus various types of oxidation may occur simultaneously.…”

Delayed Fluorescence of the Kautsky‐Müller Type from Liquid Solutions of Aromatic Compounds and Oxygen

“…Kenner and Khan [6][7][8][9] finally established the TSA mechanism {2} beyond doubt, and they concluded [6] that the delayed fluorescence observed by them was of the same type as that observed by Kautsky and Muller [2]. The importance of reaction {1} is now also firmly established due to the experimental investigations by Brauer et al [10][11][12] and others [13][14][15][16][17][18].…”