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Investigate the intramolecular radiationless decay pathways and photophysical mechanisms governing the A1A′(1B1) excited electronic state of 4-R-1,2,4-triazoline-3,5-diones.

October 1, 1974The Journal of Chemical Physics

Intramolecular energy transfer in the 4-R-1,2,4-triazoline-3,5-diones: Relation to theory and photochemical reactivity

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Authors

APAlphonsus V. Pocius3M (United States)JYJames T. YardleyUniversity of Bath

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Implication

Spectroscopic analysis demonstrates vibrational energy accelerates radiationless decay in triazolinediones, indicating triplet intersystem crossing dictates photochemical reactivity.

Key Points

Investigate the intramolecular radiationless decay pathways and photophysical mechanisms governing the A1A′(1B1) excited electronic state of 4-R-1,2,4-triazoline-3,5-diones.
Measured fluorescence lifetimes of selected vibronic levels in methyl and ethyl triazolinediones under collision-free conditions using laser-excited time-resolved fluorescence.
Determined fluorescence quantum yields and nonradiative decay rates of methyl triazolinedione across 2000 cm⁻¹ of excess vibrational energy using argon-induced vibrational relaxation.
Examined high-pressure inert gas effects on fluorescence lifetimes for methyl, ethyl, and n-butyl triazolinedione derivatives.
Collision-free fluorescence lifetimes for methyl and ethyl triazolinediones decreased linearly from ~110 to 55 nsec over 2000 cm⁻¹ of excess vibrational energy, with methyl triazolinedione exhibiting a quantum yield of ~0.02 and nonradiative rate constants increasing from 8.5×10⁶ to 16.9×10⁶ sec⁻¹.
Intersystem crossing from the excited singlet state to a lower triplet state was identified as the predominant radiationless pathway, accounting for differences in photochemical hydrogen abstraction reactivity.
Methyl, ethyl, and n-butyl derivatives all exhibited identical fluorescence lifetimes of 92±3 nsec at high inert gas pressures, providing experimental confirmation that specific vibrational modes do not participate in radiationless decay.

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Pocius et al. (1974) studied this question.

synapsesocial.com/papers/6a9fc4482b20d2a10cd4bb65 https://doi.org/10.1063/1.1682412

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Implication

Spectroscopic analysis demonstrates vibrational energy accelerates radiationless decay in triazolinediones, indicating triplet intersystem crossing dictates photochemical reactivity.

Intramolecular energy transfer in the 4-R-1,2,4-triazoline-3,5-diones: Relation to theory and photochemical reactivity

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Cite This Study

Intramolecular energy transfer in the 4-R-1,2,4-triazoline-3,5-diones: Relation to theory and photochemical reactivity

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Cite This Study

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