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Biosynthesis of a Flavonol from a Flavanone by Establishing a One-pot Bienzymatic Cascade
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Published on: August 14, 2019

Spin-forbidden transitions in flavone.

Christel M Marian1

  • 1Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany. Christel.Marian@uni-duesseldorf.de

Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
|March 7, 2009
PubMed
Summary
This summary is machine-generated.

Quantum chemical methods reveal flavone

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Area of Science:

  • Photochemistry
  • Quantum Chemistry
  • Molecular Spectroscopy

Background:

  • Flavone's electronic structure and excited states are crucial for understanding its photochemical properties.
  • Investigating intersystem crossing (ISC) and phosphorescence is key to elucidating photophysical pathways.

Purpose of the Study:

  • To investigate the ground and low-lying excited electronic states of flavone using advanced quantum chemical methods.
  • To compute spectral properties, intersystem crossing rates, and phosphorescence lifetimes.

Main Methods:

  • Utilized (time-dependent) Kohn-Sham density functional theory for structure determination.
  • Employed a combined density functional and multi-reference configuration interaction (DFT/MRCI) method for spectral properties.
  • Calculated intersystem crossing rate constants using a discretized Fermi golden rule approach and phosphorescence lifetimes via DFT/MRSOCI.

Main Results:

  • Determined ground state phenyl ring twist of 28 degrees; excited states are nearly planar or V-shaped.
  • Calculations show the T1 state has dominant pi pi* character.
  • Computed a high S1-->T1 intersystem crossing rate (kISC ≈ 3x10^11 s⁻¹) and a long T1 phosphorescence lifetime (τP ≈ 4 s).

Conclusions:

  • Large spin-orbit coupling and small energy gap between S1 and T1 states drive rapid intersystem crossing.
  • The predicted long T1 lifetime aligns with low-temperature experimental observations.
  • Nonradiative processes significantly shorten triplet flavone's lifetime in fluid solutions.