Dynamics of the second excited singlet state of thiophosgene in solution

Falk, K. J.; Sveinson, S. E.; Steer, Ronald P.

doi:10.1016/0009-2614(89)85174-7

Cited by 10 publications

(14 citation statements)

References 26 publications

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“…We therefore conclude that the difference is due to a much larger rate of nonradiative decay in media other than perfluoroalkanes. This conclusion is in full agreement with our previous inferences based on measurements of +f alone (6,7). Embedding C12CS in any solvent therefore induces radiationless decay of the B" state at rates which are much faster than those of its radiative decay and which are strongly solvent dependent.…”

Section: 00supporting

confidence: 91%

“…Thus, only short extrapolations were required to obtain +f = 2.4 x lo4 in CC14 and +f = 1.9 x lo4 in n-hexane at infinite dilution where neither self-quenching nor self-association occur. The values of +f are much smaller in CC14 and n-hexane than those in perfluoroalkanes (6), and appear to scale in about the same proportions as the lifetimes. We therefore conclude that the difference is due to a much larger rate of nonradiative decay in media other than perfluoroalkanes.…”

Section: 00mentioning

confidence: 88%

“…When the relaxation of only monomeric C12CS (B") is untangled from these complications, one finds that, in contrast to the isolated molecule, radiationless processes account for a very large fraction of decay events in solution at room temperature even when bound portions of the B state are initially populated. More importantly, the radiationless decay rates of these lowlying, apparently bound, levels of the B" state are found to be strongly dependent on the nature of the solvent (6,7). By measuring the decay rates of vibrationally thermalizedB" states as a function of temperature in dilute, weakly interacting perfluoroalkane solutions we showed (7) that the nonradiative relaxation process exhibits an effective activation energy, E,, of 1430 ?…”

Section: Introduction Atomic Species Both In the Isolated Moleculementioning

confidence: 94%

“…Thiophosgene, CI2CS, has been studied extensively both in the gas phase and in solution because it offers insight into several important aspects of electronic spectroscopy, photophysics, and photoch_emistry (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). We have been particularly interested in the B ('A') state of C12CS, which can relax by a relatively large number of possible parallel and sequential processes and therefore provides a challenging level of complexity.…”

Section: Introduction Atomic Species Both In the Isolated Moleculementioning

confidence: 99%

“…This value is nearly identical to the vibrational energy of theB" state at the onset of the fluorescence weakening process seen in the isolated molecule. In more strongly interacting n-hexane or CC14 solutions, however, the quantum yields of 8-2 fluoresc_ence are much smaller (6), from which one may infer that theB state lifetimes are much shorter than in perfluoroalkanes.…”

Section: Introduction Atomic Species Both In the Isolated Moleculementioning

confidence: 99%

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Evidence of a solvent-mediated barrier to radiationless decay in the state of thiophosgene in solution

Li¹,

Steer²

1995

Can. J. Chem.

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Thiophosgene, C12CS, has been excited in the near-uv and the resulting quantum yields of fluorescence and of CI2CS consumption have been measured as a function of solvent composition (perfluoro-nhexane, n-hexane, CC14), temperature, and excitation wavelength. In agreement with previous work it is shown that (i) nonradiative processes dominate the decay of the B state in solution, and (ii) perfluoroalkane solvents act as inert "heat baths". The process by which the B state is apparently "quenched" by CC14 and rr-hexane has been discovered. The nonradiative process leading to B's decay involves activation and crossing a barrier, the height of which is a function of the nature and composition of the solvent. CC14 and n-hexane do not quench the excited state, but instead accelerate its rate of relaxation by lowering the barrier between the bound, radiative portion of the surface and a dark, unbound region. There is evidence that CC14 or 11-hexane form clusters around a C12CS solute molecule in mixed perfluoroalkane-CCI4 or rl-hexane solutions. Barrier crossing leads to photodecomposition via at least two parallel paths, one free radical (CI + ClCS) and the other likely molecular (C12 + CS), the relative contributions of which are a function of excitation wavelength. Key worc1.s: thiophosgene, photochemistry, solvent-mediated banier crossing.Resume : On a excitC le thiophosgkne, C12CS, dans le proche-uv et on a mesure les rendements quantiques de la fluorescenceB-2 et de la consommation du CI2CS qui en resultent en fonction de la composition du solvant (perfluoro-n-hexane, n-hexane et CC14), de la tempkrature et de la longueur d'onde de I'excitation. En accord avec les travaux antkrieurs, il est dCmontrC que (i) les processus non dissociatifs dominent la dCgtntrescence de 1'Ctat Ben solution et (ii) les solvants perfluoroalcanes agissent comme des "bains de chaleur" inertes. On a dtcouvert le processus par lequel I'Ctat Best apparemment dCsactivC par le CCl4 et par le n-hexane. Le processus non radiatif conduisant h la dCgCnCrescence de B implique une activation et le passage d'une barrikre dont la hauteur est une fonction de la nature et de la composition du solvant. Le CC14 et le n-hexane ne dtsactivent pas 1'Ctat excitC, mais ils accClkrent plut8t sa vitesse de relaxation en abaissant la barrikre entre la portion radiative like de la surface et la region noire non liCe. 11 existe des indications j . l'effet que le CC14 ou le n-hexane forment des agrCgats autour d'une molCcule de CI2CS en solution dans des mClanges de perfluoroalcane, CC14 ou n-hexane. Le passage d'une barrikre conduit h une photodCcomposition par le biais d'au moins deux voies paralleles, une impliquant un radical libre (C1+ CICS) et I'autre Ctant probablement molCculaire (CI2 + CS); les contributions relatives des deux sont fonction de la longueur d'onde d'excitation.Mots cles : thiophosgkne, photochimie, passage de barrikre dCterminC par solvent.[Traduit par la ridaction]

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Section: 00supporting

confidence: 91%

Section: 00mentioning

confidence: 88%

Section: Introduction Atomic Species Both In the Isolated Moleculementioning

confidence: 94%

Section: Introduction Atomic Species Both In the Isolated Moleculementioning

confidence: 99%

Section: Introduction Atomic Species Both In the Isolated Moleculementioning

confidence: 99%

See 3 more Smart Citations

Evidence of a solvent-mediated barrier to radiationless decay in the state of thiophosgene in solution

Li¹,

Steer²

1995

Can. J. Chem.

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Spectral and Photophysical Properties of Aromatic Thiones in Micellar Systems: Xanthione as Convenient Absorption and Emission Probes

Maciejewski

Jakubowska

Dutkiewicz

et al. 1996

Journal of Colloid and Interface Science

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The laser-induced fluorescence excitation spectrum of jet-cooled Cl2CS: Origin location and partial vibronic analysis

Ludwiczak

Latimer

Steer

1991

Journal of Molecular Spectroscopy

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Dynamics of the second excited singlet state of thiophosgene in solution

Cited by 10 publications

References 26 publications

Evidence of a solvent-mediated barrier to radiationless decay in the state of thiophosgene in solution

Evidence of a solvent-mediated barrier to radiationless decay in the state of thiophosgene in solution

Spectral and Photophysical Properties of Aromatic Thiones in Micellar Systems: Xanthione as Convenient Absorption and Emission Probes

The laser-induced fluorescence excitation spectrum of jet-cooled Cl2CS: Origin location and partial vibronic analysis

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