Phosphorescence and the Triplet State

Lewis, Gilbert N.; Kasha, Michael

doi:10.1021/ja01240a030

Cited by 752 publications

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“…But another factor involved is the time the molecules remain able to react after being activated by a quantum of light. In the solid state the dye molecules may, after capture of a quantum, enter into a very long lived phosphorescent state which Lewis et al (1944Lewis et al ( , 1945 identify as a triplet or bi-radical. There may be other long lived intermediate states, and at low temperatures in the solid or semisolid state the low frequency of molecular encounters may be compensated to a certain extent by increase in the length of time the molecules remain able to react.…”

Section: Discussionmentioning

confidence: 99%

Photodynamic Hemolysis at Low Temperatures

Blum

Kauzmann

1954

Journal of General Physiology

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A large number of organic dyes may act as photosensitizers for oxidations by molecular oxygen; the substrate may be any one of a wide variety of organic or inorganic substances. When such photosensitized oxidation takes place in living systems it is commonly referred to as photodynamic action; the results are generally destructive. The name photodynamic action is not altogether appropriate since it seems to assign too general significance to the phenomenon. The term photooxidation, on the other hand, may be confusing since these same dyes may forward other photooxidations that do not produce the destructive effects characteristic of photodynamic action (see Blum, 1941).In photosensitized oxidation the dye is the light absorber, but how the energy of the absorbed quantum is employed in bringing about the oxidation of the substrate by molecular oxygen is not clearly understood. The over-all reaction may be written in the following wayin which D is the dye molecule, X the substmte, and Xoz the oxidized substrate after reacting with 02. The symbol hl is used to indicate that it is the dye molecule which captures the light quantum, but without commitment as to the way in which the energy of the quantum is used in forwarding the oxidation. D appears on the right hand side of the equation, indicating that the dye is unchanged at the end of the reaction, which may go in a cycle, the dye capturing successive quanta and repeatedly bringing about the oxidation of X molecnles by O, molecules. The evidence that a cycle occurs is very good. In simple inorganic solution the dye may photooxidize many times its equivalent of oxidizable substrate, say iodide ion. This is not a chain reaction; the quantum yield approaches but never exceeds unity. In the case of photodynamic hemolysis the same number of quanta must be absorbed per red cell by the dye (~---10 '° quanta per cell) in order to produce hemolysis, regardless of the concentration of the dye or the * Hemolysis by photosensitized oxidation. :~ Present address:

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Section: Discussionmentioning

confidence: 99%

Photodynamic Hemolysis at Low Temperatures

Blum

Kauzmann

1954

Journal of General Physiology

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“…Precise experimental details are given elsewhere (Lewis and Kasha, 1944 Moodie and Reid, 1952). The emission spectra which yielded most results of interest were obtained by dissolving (or suspending, in the case of the heterogeneous systems, examined) the carcinogen in an inert aliphatic medium which could be frozen to a clear transparent glass at the temperature of liquid nitrogen (-190' C.).…”

Section: Methodsmentioning

confidence: 99%

“…Ease of photoxidation (Cook and Martin, 1940), electronic spectra (Miller and Baumann, 1943), polarizability, free valence at a particular atom, bond order of a particular bond (in so-called K region), (PuRman, 1947), selfpolarizability (Greenwood, 1951) are typical examples.We have examined the visible and ultra-violet spectra in absorption and emission of a large number of closely related carcinogens and have attempted to correlate them with carcinogenic power. We have also examined various spectral properties depending on the degree of interaction of the carcinogen with other molecules .in its vicinity, since the initial step in the chain of events re-sulting in carcinog'enesis must involve some such interaction.…”

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confidence: 99%

“…Fluorescence spectra were traced photoelectrically using a Hilger E2 spectrograph equipped with a Scanning Unit. Phosphorescence spectra were photographed using a mechanical phosphorescope as described elsewhere (Lewis and Kasha, 1944; Moodie and Reid, 1952). Both solvents and carcinogens were purified by repeated distillation and chromatogTaphy where necessary.…”

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confidence: 99%

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confidence: 99%

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Correlation of Spectral Shifts and Carcinogenic Power

Moodie¹,

Reid²

1954

Br J Cancer

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MANY attempts have been made to relate the carcinogenic activity of aromatic bych'-ocarbons to measured and calculated physical properties with very little success. Ease of photoxidation (Cook and Martin, 1940), electronic spectra (Miller and Baumann, 1943), polarizability, free valence at a particular atom, bond order of a particular bond (in so-called K region), (PuRman, 1947), selfpolarizability (Greenwood, 1951) are typical examples.We have examined the visible and ultra-violet spectra in absorption and emission of a large number of closely related carcinogens and have attempted to correlate them with carcinogenic power. We have also examined various spectral properties depending on the degree of interaction of the carcinogen with other molecules .in its vicinity, since the initial step in the chain of events re-sulting in carcinog'enesis must involve some such interaction. EXPERIMENTAL.Precise experimental details are given elsewhere (Lewis and Kasha, 1944 Moodie and Reid, 1952). The emission spectra which yielded most results of interest were obtained by dissolving (or suspending, in the case of the heterogeneous systems, examined) the carcinogen in an inert aliphatic medium which could be frozen to a clear transparent glass at the temperature of liquid nitrogen (-190' C.). The samples were frozen in cyhndrical tubes immersed in a quartz Dewar vessel and were irradiated with filtered light from a high pressure mercury arc, either the 3100 A or the 3650 A group of hnes being used. Under these conditions afl the molecules examined were strongly luminescent, showing both a short-lived fluorescence (persisting for less than 10-8 seconds) and longhved phosphorescence (persisting for several seconds) in different spectral regions. Fluorescence spectra were traced photoelectrically using a Hilger E2 spectrograph equipped with a Scanning Unit. Phosphorescence spectra were photographed using a mechanical phosphorescope as described elsewhere (Lewis and Kasha, 1944; Moodie and Reid, 1952). Both solvents and carcinogens were purified by repeated distillation and chromatogTaphy where necessary.RESULTS AND DISCUSSION.(1) No significant correlation could be found between absorption or short-lived spectra and carcinogenic activity, and these spectra, which have already been considered by other workers, wiR not be discussed. However, some correlations

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