Spectroscopic properties of aromatic dicarboximides. Part 4. On the modification of the fluorescence and intersystem crossing processes of molecules by electron-donating methoxy groups at different positions. The case of 1,8-naphthalimides

Véronique Wintgens, Pierre Valat, Jean Kossanyi, A. Demeter, L. Biczók, T. Bérces

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Abstract

N-Phenyl-1,8-naphthalimide shows almost no fluorescence emission and a low (ca 0.1) intersystem crossing quantum yield. Its photophysical properties can be drastically varied by methoxy substitution at different locations of the molecule: (i) when it is at the para position of the N-phenyl ring, the fluorescence remains weak but is red-shifted by 70 to 200 nm and, at the same time, the intersystem crossing quantum yield increases by a factor of five; (ii) when the methoxy group is at the 4-position on the naphthalene ring, the fluorescence quantum yield increases to 0.87 in acetonitrile with a concomitant increase of the singlet excited state lifetime to 9.0 ns and a consequent drop of the intersystem crossing yield. The effect is less pronounced in hexane solution. However, methoxy substitution at both positions increases the intersystem crossing quantum yield and induces dual luminescence, which is solvent dependent. The triplet excited state has been characterized by phosphorescence emission and by triplet-triplet absorption. The energy of the lowest triplet excited state appears to be independent of the substitution, whether on the dicarboximide nitrogen atom or at the 4-position of the naphthalene ring. All the spectroscopic changes observed with substitution have been tentatively rationalized from the modification of the energy levels: (i) of the close-lying S1 and S2 states (having π,π* and charge-transfer character, respectively) and (ii) of an upper n,π* triplet state.

Original languageEnglish
Pages (from-to)1149-1158
Number of pages10
JournalNew Journal of Chemistry
Volume20
Issue number11
Publication statusPublished - 1996

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Naphthalimides
Quantum yield
Substitution reactions
Fluorescence
Excited states
Molecules
Electrons
Naphthalene
Phosphorescence
Hexanes
Hexane
Acetonitrile
Electron energy levels
Charge transfer
Luminescence
Nitrogen
Atoms

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Spectroscopic properties of aromatic dicarboximides. Part 4. On the modification of the fluorescence and intersystem crossing processes of molecules by electron-donating methoxy groups at different positions. The case of 1,8-naphthalimides",
abstract = "N-Phenyl-1,8-naphthalimide shows almost no fluorescence emission and a low (ca 0.1) intersystem crossing quantum yield. Its photophysical properties can be drastically varied by methoxy substitution at different locations of the molecule: (i) when it is at the para position of the N-phenyl ring, the fluorescence remains weak but is red-shifted by 70 to 200 nm and, at the same time, the intersystem crossing quantum yield increases by a factor of five; (ii) when the methoxy group is at the 4-position on the naphthalene ring, the fluorescence quantum yield increases to 0.87 in acetonitrile with a concomitant increase of the singlet excited state lifetime to 9.0 ns and a consequent drop of the intersystem crossing yield. The effect is less pronounced in hexane solution. However, methoxy substitution at both positions increases the intersystem crossing quantum yield and induces dual luminescence, which is solvent dependent. The triplet excited state has been characterized by phosphorescence emission and by triplet-triplet absorption. The energy of the lowest triplet excited state appears to be independent of the substitution, whether on the dicarboximide nitrogen atom or at the 4-position of the naphthalene ring. All the spectroscopic changes observed with substitution have been tentatively rationalized from the modification of the energy levels: (i) of the close-lying S1 and S2 states (having π,π* and charge-transfer character, respectively) and (ii) of an upper n,π* triplet state.",
author = "V{\'e}ronique Wintgens and Pierre Valat and Jean Kossanyi and A. Demeter and L. Bicz{\'o}k and T. B{\'e}rces",
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T1 - Spectroscopic properties of aromatic dicarboximides. Part 4. On the modification of the fluorescence and intersystem crossing processes of molecules by electron-donating methoxy groups at different positions. The case of 1,8-naphthalimides

AU - Wintgens, Véronique

AU - Valat, Pierre

AU - Kossanyi, Jean

AU - Demeter, A.

AU - Biczók, L.

AU - Bérces, T.

PY - 1996

Y1 - 1996

N2 - N-Phenyl-1,8-naphthalimide shows almost no fluorescence emission and a low (ca 0.1) intersystem crossing quantum yield. Its photophysical properties can be drastically varied by methoxy substitution at different locations of the molecule: (i) when it is at the para position of the N-phenyl ring, the fluorescence remains weak but is red-shifted by 70 to 200 nm and, at the same time, the intersystem crossing quantum yield increases by a factor of five; (ii) when the methoxy group is at the 4-position on the naphthalene ring, the fluorescence quantum yield increases to 0.87 in acetonitrile with a concomitant increase of the singlet excited state lifetime to 9.0 ns and a consequent drop of the intersystem crossing yield. The effect is less pronounced in hexane solution. However, methoxy substitution at both positions increases the intersystem crossing quantum yield and induces dual luminescence, which is solvent dependent. The triplet excited state has been characterized by phosphorescence emission and by triplet-triplet absorption. The energy of the lowest triplet excited state appears to be independent of the substitution, whether on the dicarboximide nitrogen atom or at the 4-position of the naphthalene ring. All the spectroscopic changes observed with substitution have been tentatively rationalized from the modification of the energy levels: (i) of the close-lying S1 and S2 states (having π,π* and charge-transfer character, respectively) and (ii) of an upper n,π* triplet state.

AB - N-Phenyl-1,8-naphthalimide shows almost no fluorescence emission and a low (ca 0.1) intersystem crossing quantum yield. Its photophysical properties can be drastically varied by methoxy substitution at different locations of the molecule: (i) when it is at the para position of the N-phenyl ring, the fluorescence remains weak but is red-shifted by 70 to 200 nm and, at the same time, the intersystem crossing quantum yield increases by a factor of five; (ii) when the methoxy group is at the 4-position on the naphthalene ring, the fluorescence quantum yield increases to 0.87 in acetonitrile with a concomitant increase of the singlet excited state lifetime to 9.0 ns and a consequent drop of the intersystem crossing yield. The effect is less pronounced in hexane solution. However, methoxy substitution at both positions increases the intersystem crossing quantum yield and induces dual luminescence, which is solvent dependent. The triplet excited state has been characterized by phosphorescence emission and by triplet-triplet absorption. The energy of the lowest triplet excited state appears to be independent of the substitution, whether on the dicarboximide nitrogen atom or at the 4-position of the naphthalene ring. All the spectroscopic changes observed with substitution have been tentatively rationalized from the modification of the energy levels: (i) of the close-lying S1 and S2 states (having π,π* and charge-transfer character, respectively) and (ii) of an upper n,π* triplet state.

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