Intramolecular photoassociation and photoinduced charge transfer in bridged diaryl compounds. 7. A semiempirical MO study of intramolecular charge transfer in the excited singlet states of dinaphthylamines

D. Chen, Rovshan Sadygov, E. C. Lim

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Abstract

A semiempirical MO study of the intramolecular charge transfer (CT) in the excited singlet states of dinaphthylamines has been carried out with the program systems MOPAC and ARGUS. The excited-state energies for various conformations of the molecules were obtained, in both the absence and the presence of a polarizable medium, by adding the transition energies calculated with the INDO I/S method to the ground-state energies calculated by means of the AM1 method. The CT state corresponds to a twisted geometry in which one naphthalene moiety is conjugated with the amino bridge, while the other moiety is perpendicular to the first. The gas-phase energy of this twisted intramolecular CT (TICT) state is only slightly greater than that of the lowest excited singlet (S1) state of smaller dipole moment. In solvent of large dielectric constant, the TICT state is therefore predicted to be the lowest excited singlet state of the module. The computed oscillator strength of the absorption to the TICT state is much smaller than that to the lowest-energy excited state of an isolated molecule, so that the increase CT character of the S1 state in polar solvents is expected to lead to a decrease in the radiative decay rate of the state. These results are consistent with the experimental observation of a large fluorescence Stokes shift, and a reduction in the S1 radiative decay rate, of the compounds in polar solvents relative to nonpolar solvents.

Original languageEnglish (US)
Pages (from-to)2018-2023
Number of pages6
JournalJournal of Physical Chemistry
Volume98
Issue number8
StatePublished - Jan 1 1994
Externally publishedYes

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Excited states
Charge transfer
charge transfer
excitation
decay rates
Molecules
energy
Dipole moment
Naphthalene
Ground state
Conformations
Permittivity
naphthalene
Gases
oscillator strengths
Fluorescence
molecules
dipole moments
modules
Geometry

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

Cite this

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title = "Intramolecular photoassociation and photoinduced charge transfer in bridged diaryl compounds. 7. A semiempirical MO study of intramolecular charge transfer in the excited singlet states of dinaphthylamines",
abstract = "A semiempirical MO study of the intramolecular charge transfer (CT) in the excited singlet states of dinaphthylamines has been carried out with the program systems MOPAC and ARGUS. The excited-state energies for various conformations of the molecules were obtained, in both the absence and the presence of a polarizable medium, by adding the transition energies calculated with the INDO I/S method to the ground-state energies calculated by means of the AM1 method. The CT state corresponds to a twisted geometry in which one naphthalene moiety is conjugated with the amino bridge, while the other moiety is perpendicular to the first. The gas-phase energy of this twisted intramolecular CT (TICT) state is only slightly greater than that of the lowest excited singlet (S1) state of smaller dipole moment. In solvent of large dielectric constant, the TICT state is therefore predicted to be the lowest excited singlet state of the module. The computed oscillator strength of the absorption to the TICT state is much smaller than that to the lowest-energy excited state of an isolated molecule, so that the increase CT character of the S1 state in polar solvents is expected to lead to a decrease in the radiative decay rate of the state. These results are consistent with the experimental observation of a large fluorescence Stokes shift, and a reduction in the S1 radiative decay rate, of the compounds in polar solvents relative to nonpolar solvents.",
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T1 - Intramolecular photoassociation and photoinduced charge transfer in bridged diaryl compounds. 7. A semiempirical MO study of intramolecular charge transfer in the excited singlet states of dinaphthylamines

AU - Chen, D.

AU - Sadygov, Rovshan

AU - Lim, E. C.

PY - 1994/1/1

Y1 - 1994/1/1

N2 - A semiempirical MO study of the intramolecular charge transfer (CT) in the excited singlet states of dinaphthylamines has been carried out with the program systems MOPAC and ARGUS. The excited-state energies for various conformations of the molecules were obtained, in both the absence and the presence of a polarizable medium, by adding the transition energies calculated with the INDO I/S method to the ground-state energies calculated by means of the AM1 method. The CT state corresponds to a twisted geometry in which one naphthalene moiety is conjugated with the amino bridge, while the other moiety is perpendicular to the first. The gas-phase energy of this twisted intramolecular CT (TICT) state is only slightly greater than that of the lowest excited singlet (S1) state of smaller dipole moment. In solvent of large dielectric constant, the TICT state is therefore predicted to be the lowest excited singlet state of the module. The computed oscillator strength of the absorption to the TICT state is much smaller than that to the lowest-energy excited state of an isolated molecule, so that the increase CT character of the S1 state in polar solvents is expected to lead to a decrease in the radiative decay rate of the state. These results are consistent with the experimental observation of a large fluorescence Stokes shift, and a reduction in the S1 radiative decay rate, of the compounds in polar solvents relative to nonpolar solvents.

AB - A semiempirical MO study of the intramolecular charge transfer (CT) in the excited singlet states of dinaphthylamines has been carried out with the program systems MOPAC and ARGUS. The excited-state energies for various conformations of the molecules were obtained, in both the absence and the presence of a polarizable medium, by adding the transition energies calculated with the INDO I/S method to the ground-state energies calculated by means of the AM1 method. The CT state corresponds to a twisted geometry in which one naphthalene moiety is conjugated with the amino bridge, while the other moiety is perpendicular to the first. The gas-phase energy of this twisted intramolecular CT (TICT) state is only slightly greater than that of the lowest excited singlet (S1) state of smaller dipole moment. In solvent of large dielectric constant, the TICT state is therefore predicted to be the lowest excited singlet state of the module. The computed oscillator strength of the absorption to the TICT state is much smaller than that to the lowest-energy excited state of an isolated molecule, so that the increase CT character of the S1 state in polar solvents is expected to lead to a decrease in the radiative decay rate of the state. These results are consistent with the experimental observation of a large fluorescence Stokes shift, and a reduction in the S1 radiative decay rate, of the compounds in polar solvents relative to nonpolar solvents.

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