Ultrafast intramolecular charge transfer and internal conversion with tetrafluoro-aminobenzonitriles

Victor A. Galievsky, Sergey I. Druzhinin, A. Demeter, Yun Bao Jiang, Sergey A. Kovalenko, Luis Pérez Lustres, Karunakaran Venugopal, Nikolaus P. Ernsting, Xavier Allonas, Mathias Noltemeyer, Reinhard Machinek, Klaas A. Zachariasse

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

The five 2,3,5,6-tetrafluoro-4-aminobenzonitriles XABN4F with a dimethyl-amino (DMABN4F), diethyl-amino (DEABN4F), azetidinyl (AZABN4F), methyl-amino (MABN4F) or amino (ABN4F) group undergo ultrafast intramolecular charge transfer (ICT) at room temperature, in the polar solvent acetonitrile (MeCN) as well as in the nonpolar n-hexane. ICT also takes place with the corresponding non-fluorinated aminobenzonitriles DMABN, DEABN and AZABN in MeCN, whereas for these molecules in n-hexane only minor (DMABN, DEABN) or no (AZABN) ICT fluorescence is detected. For the secondary (MABN) and primary (ABN) amines, an ICT reaction does not occur, which makes ABN4F the first electron donor/acceptor molecule with an NH2 group for which ICT is observed. The ICT state of the XABN4Fs has a dipole moment of around 14 D, clearly smaller than that of DMABN (17 D). This difference is attributed to the electron withdrawing from the CN group to the phenyl ring, exerted by the four F-substituents. The reaction from the initially prepared locally excited (LE) to the ICT state in n-hexane proceeds in the sub-picosecond time range: 0.35 ps (DMABN4F), 0.29 ps (DEABN4F) and 0.13 ps (AZABN4F), as determined from femtosecond transient absorption measurements. In the highly polar solvent MeCN, an ICT reaction time of around 90 fs is observed for all five XABN4Fs, irrespective of the nature of their amino group. This shows that with these molecules in MeCN the ICT reaction rate is limited by the solvent dielectric relaxation time of MeCN, for which a value of around 90 fs has been reported. It is therefore concluded that, during this ultrashort ICT reaction, a large-amplitude motion such as a full 90° twist of the amino group is unlikely to occur in the XABN4Fs. The ICT state of the XABN4Fs is strongly quenched via internal conversion (IC), with a lifetime τ′ 0(ICT) down to 3 ps, possibly by a reaction passing through a conical intersection made accessible due to a deformation of the phenyl group by out-of-plane motions induced by vibronic coupling between low-lying πσ* and ππ* states in the XABN4Fs.

Original languageEnglish
Pages (from-to)2307-2323
Number of pages17
JournalChemPhysChem
Volume6
Issue number11
DOIs
Publication statusPublished - Nov 11 2005

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internal conversion
Charge transfer
charge transfer
Molecules
molecules
Electrons
Dielectric relaxation
Dipole moment
reaction time
Relaxation time
intersections
Reaction rates
acetonitrile
Amines
amines
reaction kinetics
dipole moments
electrons
relaxation time
Fluorescence

Keywords

  • Charge transfer
  • Femtochemistry
  • Femtosecond transient absorption
  • Fluorescence
  • Internal conversion

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Galievsky, V. A., Druzhinin, S. I., Demeter, A., Jiang, Y. B., Kovalenko, S. A., Pérez Lustres, L., ... Zachariasse, K. A. (2005). Ultrafast intramolecular charge transfer and internal conversion with tetrafluoro-aminobenzonitriles. ChemPhysChem, 6(11), 2307-2323. https://doi.org/10.1002/cphc.200500267

Ultrafast intramolecular charge transfer and internal conversion with tetrafluoro-aminobenzonitriles. / Galievsky, Victor A.; Druzhinin, Sergey I.; Demeter, A.; Jiang, Yun Bao; Kovalenko, Sergey A.; Pérez Lustres, Luis; Venugopal, Karunakaran; Ernsting, Nikolaus P.; Allonas, Xavier; Noltemeyer, Mathias; Machinek, Reinhard; Zachariasse, Klaas A.

In: ChemPhysChem, Vol. 6, No. 11, 11.11.2005, p. 2307-2323.

Research output: Contribution to journalArticle

Galievsky, VA, Druzhinin, SI, Demeter, A, Jiang, YB, Kovalenko, SA, Pérez Lustres, L, Venugopal, K, Ernsting, NP, Allonas, X, Noltemeyer, M, Machinek, R & Zachariasse, KA 2005, 'Ultrafast intramolecular charge transfer and internal conversion with tetrafluoro-aminobenzonitriles', ChemPhysChem, vol. 6, no. 11, pp. 2307-2323. https://doi.org/10.1002/cphc.200500267
Galievsky VA, Druzhinin SI, Demeter A, Jiang YB, Kovalenko SA, Pérez Lustres L et al. Ultrafast intramolecular charge transfer and internal conversion with tetrafluoro-aminobenzonitriles. ChemPhysChem. 2005 Nov 11;6(11):2307-2323. https://doi.org/10.1002/cphc.200500267
Galievsky, Victor A. ; Druzhinin, Sergey I. ; Demeter, A. ; Jiang, Yun Bao ; Kovalenko, Sergey A. ; Pérez Lustres, Luis ; Venugopal, Karunakaran ; Ernsting, Nikolaus P. ; Allonas, Xavier ; Noltemeyer, Mathias ; Machinek, Reinhard ; Zachariasse, Klaas A. / Ultrafast intramolecular charge transfer and internal conversion with tetrafluoro-aminobenzonitriles. In: ChemPhysChem. 2005 ; Vol. 6, No. 11. pp. 2307-2323.
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abstract = "The five 2,3,5,6-tetrafluoro-4-aminobenzonitriles XABN4F with a dimethyl-amino (DMABN4F), diethyl-amino (DEABN4F), azetidinyl (AZABN4F), methyl-amino (MABN4F) or amino (ABN4F) group undergo ultrafast intramolecular charge transfer (ICT) at room temperature, in the polar solvent acetonitrile (MeCN) as well as in the nonpolar n-hexane. ICT also takes place with the corresponding non-fluorinated aminobenzonitriles DMABN, DEABN and AZABN in MeCN, whereas for these molecules in n-hexane only minor (DMABN, DEABN) or no (AZABN) ICT fluorescence is detected. For the secondary (MABN) and primary (ABN) amines, an ICT reaction does not occur, which makes ABN4F the first electron donor/acceptor molecule with an NH2 group for which ICT is observed. The ICT state of the XABN4Fs has a dipole moment of around 14 D, clearly smaller than that of DMABN (17 D). This difference is attributed to the electron withdrawing from the CN group to the phenyl ring, exerted by the four F-substituents. The reaction from the initially prepared locally excited (LE) to the ICT state in n-hexane proceeds in the sub-picosecond time range: 0.35 ps (DMABN4F), 0.29 ps (DEABN4F) and 0.13 ps (AZABN4F), as determined from femtosecond transient absorption measurements. In the highly polar solvent MeCN, an ICT reaction time of around 90 fs is observed for all five XABN4Fs, irrespective of the nature of their amino group. This shows that with these molecules in MeCN the ICT reaction rate is limited by the solvent dielectric relaxation time of MeCN, for which a value of around 90 fs has been reported. It is therefore concluded that, during this ultrashort ICT reaction, a large-amplitude motion such as a full 90° twist of the amino group is unlikely to occur in the XABN4Fs. The ICT state of the XABN4Fs is strongly quenched via internal conversion (IC), with a lifetime τ′ 0(ICT) down to 3 ps, possibly by a reaction passing through a conical intersection made accessible due to a deformation of the phenyl group by out-of-plane motions induced by vibronic coupling between low-lying πσ* and ππ* states in the XABN4Fs.",
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T1 - Ultrafast intramolecular charge transfer and internal conversion with tetrafluoro-aminobenzonitriles

AU - Galievsky, Victor A.

AU - Druzhinin, Sergey I.

AU - Demeter, A.

AU - Jiang, Yun Bao

AU - Kovalenko, Sergey A.

AU - Pérez Lustres, Luis

AU - Venugopal, Karunakaran

AU - Ernsting, Nikolaus P.

AU - Allonas, Xavier

AU - Noltemeyer, Mathias

AU - Machinek, Reinhard

AU - Zachariasse, Klaas A.

PY - 2005/11/11

Y1 - 2005/11/11

N2 - The five 2,3,5,6-tetrafluoro-4-aminobenzonitriles XABN4F with a dimethyl-amino (DMABN4F), diethyl-amino (DEABN4F), azetidinyl (AZABN4F), methyl-amino (MABN4F) or amino (ABN4F) group undergo ultrafast intramolecular charge transfer (ICT) at room temperature, in the polar solvent acetonitrile (MeCN) as well as in the nonpolar n-hexane. ICT also takes place with the corresponding non-fluorinated aminobenzonitriles DMABN, DEABN and AZABN in MeCN, whereas for these molecules in n-hexane only minor (DMABN, DEABN) or no (AZABN) ICT fluorescence is detected. For the secondary (MABN) and primary (ABN) amines, an ICT reaction does not occur, which makes ABN4F the first electron donor/acceptor molecule with an NH2 group for which ICT is observed. The ICT state of the XABN4Fs has a dipole moment of around 14 D, clearly smaller than that of DMABN (17 D). This difference is attributed to the electron withdrawing from the CN group to the phenyl ring, exerted by the four F-substituents. The reaction from the initially prepared locally excited (LE) to the ICT state in n-hexane proceeds in the sub-picosecond time range: 0.35 ps (DMABN4F), 0.29 ps (DEABN4F) and 0.13 ps (AZABN4F), as determined from femtosecond transient absorption measurements. In the highly polar solvent MeCN, an ICT reaction time of around 90 fs is observed for all five XABN4Fs, irrespective of the nature of their amino group. This shows that with these molecules in MeCN the ICT reaction rate is limited by the solvent dielectric relaxation time of MeCN, for which a value of around 90 fs has been reported. It is therefore concluded that, during this ultrashort ICT reaction, a large-amplitude motion such as a full 90° twist of the amino group is unlikely to occur in the XABN4Fs. The ICT state of the XABN4Fs is strongly quenched via internal conversion (IC), with a lifetime τ′ 0(ICT) down to 3 ps, possibly by a reaction passing through a conical intersection made accessible due to a deformation of the phenyl group by out-of-plane motions induced by vibronic coupling between low-lying πσ* and ππ* states in the XABN4Fs.

AB - The five 2,3,5,6-tetrafluoro-4-aminobenzonitriles XABN4F with a dimethyl-amino (DMABN4F), diethyl-amino (DEABN4F), azetidinyl (AZABN4F), methyl-amino (MABN4F) or amino (ABN4F) group undergo ultrafast intramolecular charge transfer (ICT) at room temperature, in the polar solvent acetonitrile (MeCN) as well as in the nonpolar n-hexane. ICT also takes place with the corresponding non-fluorinated aminobenzonitriles DMABN, DEABN and AZABN in MeCN, whereas for these molecules in n-hexane only minor (DMABN, DEABN) or no (AZABN) ICT fluorescence is detected. For the secondary (MABN) and primary (ABN) amines, an ICT reaction does not occur, which makes ABN4F the first electron donor/acceptor molecule with an NH2 group for which ICT is observed. The ICT state of the XABN4Fs has a dipole moment of around 14 D, clearly smaller than that of DMABN (17 D). This difference is attributed to the electron withdrawing from the CN group to the phenyl ring, exerted by the four F-substituents. The reaction from the initially prepared locally excited (LE) to the ICT state in n-hexane proceeds in the sub-picosecond time range: 0.35 ps (DMABN4F), 0.29 ps (DEABN4F) and 0.13 ps (AZABN4F), as determined from femtosecond transient absorption measurements. In the highly polar solvent MeCN, an ICT reaction time of around 90 fs is observed for all five XABN4Fs, irrespective of the nature of their amino group. This shows that with these molecules in MeCN the ICT reaction rate is limited by the solvent dielectric relaxation time of MeCN, for which a value of around 90 fs has been reported. It is therefore concluded that, during this ultrashort ICT reaction, a large-amplitude motion such as a full 90° twist of the amino group is unlikely to occur in the XABN4Fs. The ICT state of the XABN4Fs is strongly quenched via internal conversion (IC), with a lifetime τ′ 0(ICT) down to 3 ps, possibly by a reaction passing through a conical intersection made accessible due to a deformation of the phenyl group by out-of-plane motions induced by vibronic coupling between low-lying πσ* and ππ* states in the XABN4Fs.

KW - Charge transfer

KW - Femtochemistry

KW - Femtosecond transient absorption

KW - Fluorescence

KW - Internal conversion

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