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Avoided spin coupling: an unexpected σ-σ diradical in global planar pentacoordinate carbon
Meng-Hui Wang1, Xue Dong, Yi-Hong Ding
1Institute of Atomic and Molecular Physics, Jilin University; Beijing National Laboratory for Molecular Sciences, Changchun 130012, China. zcui@jlu.edu.cn.
Chemical Communications (Cambridge, England)
|June 2, 2020
Summary
Researchers discovered a novel planar pentacoordinate carbon (ppC) with a unique σ-σ diradical nature. This C3Li3- anion exhibits a triplet ground state, differing significantly from previously known ppCs.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Materials Science
Background:
- Planar pentacoordinate carbons (ppCs) are rare structures with unique electronic properties.
- Understanding the bonding and electronic characteristics of novel ppC structures is crucial for advancing chemical bonding theories.
Purpose of the Study:
- To investigate the electronic structure and bonding characteristics of a newly identified global planar pentacoordinate carbon (ppC).
- To explore the σ-σ diradical nature and triplet ground state of the C3Li3- anion.
Main Methods:
- Utilized a multi-reference approach combined with the Coupled Cluster Singles Doubles with Perturbation Theory (CCSD(T))/aug-cc-pVTZ method.
- Performed detailed chemical bonding analysis to understand electron distribution and bonding patterns.
Main Results:
- Identified a global planar pentacoordinate carbon (ppC) with an unprecedented σ-σ diradical characteristic.
- The C3Li3- anion was found to possess a triplet ground state with unpaired electron density localized on the Li ligands.
- Unlike typical ppCs, the 2pzπ electrons in C3Li3- are confined to the C3 ring, indicating localized C-C multiple bonds.
Conclusions:
- The discovered C3Li3- represents a new class of ppC with distinct electronic and bonding features.
- The σ-σ diradical character and localized π-electron system challenge existing models of ppC bonding.
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