Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics

Martin Alex Bjørn Larsen; Jan Thøgersen; Anne Boutrup Stephansen; Jorge Peon; Theis Ivan Sølling; Søren Rud Keiding

doi:10.1021/acs.jpca.5b09125

Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics

Martin Alex Bjørn Larsen, Jan Thøgersen, Anne Boutrup Stephansen, Jorge Peon, Theis Ivan Sølling, Søren Rud Keiding

Department of Chemistry

12 Citations (Scopus)

Abstract

The dynamics of 2-nitrofluorene (2-NF) in deuterated acetonitrile is studied using UV pump, IR probe femtosecond transient absorption spectroscopy. Upon excitation to the vibrationally excited S₁ state, the excited-state population of 2-NF branches into two different relaxation pathways. One route leads to intersystem crossing (ISC) to the triplet manifold within a few hundred femtoseconds and the other to internal conversion (IC) to the ground state. The experiments indicate that after relaxation to the energetic minimum on S₁, 2-NF undergoes internal conversion to the ground state in about 15 ps. IC within the triplet manifold is also observed as the initially populated triplet state relaxes to T₁ in about 6 ps. Rotational anisotropy measurements corroborate the assignment of the transient IR frequencies and indicate a rotational diffusion time of 2-NF in the solvent of about 14 ps. The combined set of results provides a unified picture of the dynamics in photoexcited 2-NF. This to our knowledge is the first example using femtosecond vibrational spectroscopy for the study of the fundamental photoinduced processes in nitroaromatic compounds.

Original language	English
Journal	Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Volume	120
Issue number	1
Pages (from-to)	28-35
Number of pages	8
ISSN	1089-5639
DOIs	https://doi.org/10.1021/acs.jpca.5b09125
Publication status	Published - 14 Jan 2016

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Larsen, M. A. B., Thøgersen, J., Stephansen, A. B., Peon, J., Sølling, T. I., & Keiding, S. R. (2016). Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics. Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory, 120(1), 28-35. https://doi.org/10.1021/acs.jpca.5b09125

Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics. / Larsen, Martin Alex Bjørn; Thøgersen, Jan; Stephansen, Anne Boutrup et al.
In: Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory, Vol. 120, No. 1, 14.01.2016, p. 28-35.

Research output: Contribution to journal › Journal article › Research › peer-review

Larsen, MAB, Thøgersen, J, Stephansen, AB, Peon, J, Sølling, TI & Keiding, SR 2016, 'Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics', Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory, vol. 120, no. 1, pp. 28-35. https://doi.org/10.1021/acs.jpca.5b09125

Larsen MAB, Thøgersen J, Stephansen AB, Peon J, Sølling TI, Keiding SR. Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics. Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. 2016 Jan 14;120(1):28-35. doi: 10.1021/acs.jpca.5b09125

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title = "Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics",

abstract = "The dynamics of 2-nitrofluorene (2-NF) in deuterated acetonitrile is studied using UV pump, IR probe femtosecond transient absorption spectroscopy. Upon excitation to the vibrationally excited S1 state, the excited-state population of 2-NF branches into two different relaxation pathways. One route leads to intersystem crossing (ISC) to the triplet manifold within a few hundred femtoseconds and the other to internal conversion (IC) to the ground state. The experiments indicate that after relaxation to the energetic minimum on S1, 2-NF undergoes internal conversion to the ground state in about 15 ps. IC within the triplet manifold is also observed as the initially populated triplet state relaxes to T1 in about 6 ps. Rotational anisotropy measurements corroborate the assignment of the transient IR frequencies and indicate a rotational diffusion time of 2-NF in the solvent of about 14 ps. The combined set of results provides a unified picture of the dynamics in photoexcited 2-NF. This to our knowledge is the first example using femtosecond vibrational spectroscopy for the study of the fundamental photoinduced processes in nitroaromatic compounds.",

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doi = "10.1021/acs.jpca.5b09125",

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T1 - Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene

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AU - Larsen, Martin Alex Bjørn

AU - Thøgersen, Jan

AU - Stephansen, Anne Boutrup

AU - Peon, Jorge

AU - Sølling, Theis Ivan

AU - Keiding, Søren Rud

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N2 - The dynamics of 2-nitrofluorene (2-NF) in deuterated acetonitrile is studied using UV pump, IR probe femtosecond transient absorption spectroscopy. Upon excitation to the vibrationally excited S1 state, the excited-state population of 2-NF branches into two different relaxation pathways. One route leads to intersystem crossing (ISC) to the triplet manifold within a few hundred femtoseconds and the other to internal conversion (IC) to the ground state. The experiments indicate that after relaxation to the energetic minimum on S1, 2-NF undergoes internal conversion to the ground state in about 15 ps. IC within the triplet manifold is also observed as the initially populated triplet state relaxes to T1 in about 6 ps. Rotational anisotropy measurements corroborate the assignment of the transient IR frequencies and indicate a rotational diffusion time of 2-NF in the solvent of about 14 ps. The combined set of results provides a unified picture of the dynamics in photoexcited 2-NF. This to our knowledge is the first example using femtosecond vibrational spectroscopy for the study of the fundamental photoinduced processes in nitroaromatic compounds.

AB - The dynamics of 2-nitrofluorene (2-NF) in deuterated acetonitrile is studied using UV pump, IR probe femtosecond transient absorption spectroscopy. Upon excitation to the vibrationally excited S1 state, the excited-state population of 2-NF branches into two different relaxation pathways. One route leads to intersystem crossing (ISC) to the triplet manifold within a few hundred femtoseconds and the other to internal conversion (IC) to the ground state. The experiments indicate that after relaxation to the energetic minimum on S1, 2-NF undergoes internal conversion to the ground state in about 15 ps. IC within the triplet manifold is also observed as the initially populated triplet state relaxes to T1 in about 6 ps. Rotational anisotropy measurements corroborate the assignment of the transient IR frequencies and indicate a rotational diffusion time of 2-NF in the solvent of about 14 ps. The combined set of results provides a unified picture of the dynamics in photoexcited 2-NF. This to our knowledge is the first example using femtosecond vibrational spectroscopy for the study of the fundamental photoinduced processes in nitroaromatic compounds.

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JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

IS - 1

ER -

Transient IR spectroscopic observation of singlet and triplet states of 2-nitrofluorene: revisiting the photophysics of nitroaromatics

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