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A Thermally Populated, Perpendicularly Twisted Alkene Triplet Diradical
Curt Wentrup1, Michèle J Regimbald-Krnel1, Dennis Müller2
1School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.
Angewandte Chemie (International Ed. in English)
|October 21, 2016
Summary
Bis(dibenzo[a,i]fluorenylidene) 1 exhibits a singlet ground state, with a small population of its triplet state even at room temperature. Spectroscopic analysis determined key energy parameters, confirming theoretical calculations.
Area of Science:
- Organic Chemistry
- Spectroscopy
- Computational Chemistry
Background:
- Understanding the electronic properties of organic molecules is crucial for developing new materials.
- Bis(dibenzo[a,i]fluorenylidene) is a molecule of interest due to its unique structural and electronic characteristics.
Purpose of the Study:
- To investigate the ground and excited electronic states of bis(dibenzo[a,i]fluorenylidene) 1.
- To determine the singlet-triplet energy gap and exchange interaction of the molecule.
Main Methods:
- Variable-temperature Nuclear Magnetic Resonance (NMR) spectroscopy.
- Electron Spin Resonance (ESR) spectroscopy.
- Quantum chemical calculations (UKS BP86/B3LYP/revPBE).
Main Results:
- Bis(dibenzo[a,i]fluorenylidene) 1 was found to possess a singlet ground state (1(S0)).
- A small population of the twisted triplet state (1(T1)) was observed at room temperature.
- The singlet-triplet energy splitting was determined to be 9.6 kcal/mol, closely matching computational predictions (9.3 kcal/mol).
- The exchange interaction (Jex/hc) was calculated to be 3351 cm-1.
- The zero-field splitting parameter D was found to be very small and unmeasurable.
Conclusions:
- The study confirms the singlet ground state of bis(dibenzo[a,i]fluorenylidene) 1.
- Variable-temperature NMR and ESR spectroscopy provide valuable insights into the electronic structure and energy levels of organic molecules.
- Computational methods accurately predict the energetic properties of this compound.
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