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Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
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Computational Studies of Dimerization of [n]-Cyclacenes
Ankit Somani1, Divanshu Gupta1, Holger F Bettinger1
1Institut für Organische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, Tübingen 72076, Germany.
The Journal of Physical Chemistry. A
|August 12, 2024
Summary
Cyclacenes, cyclic versions of acenes, are predicted to dimerize, a key degradation pathway. Dimerization energy increases with size but is affected by strain and cryptoannulenic effects.
Area of Science:
- Organic Chemistry
- Materials Science
- Computational Chemistry
Background:
- Cyclacenes are nanohoop structures composed of linearly fused benzene rings.
- They represent cyclic analogs of acenes and have not yet been synthesized.
- Dimerization is a potential degradation pathway for cyclacenes under oxygen-free conditions.
Purpose of the Study:
- To estimate the tendency of [n]-cyclacenes (n=6-20) to undergo dimerization.
- To compute the energy of dimerization for various cyclacene sizes.
- To understand the factors influencing cyclacene dimerization.
Main Methods:
- Density Functional Theory (DFT) calculations were employed.
- Spin-restricted, spin-unrestricted, and thermally assisted-occupation (TAO) formalisms were utilized.
- Computational methods were used to determine dimerization energies.
Main Results:
- The energy of dimerization increases with the size (n) of the cyclacene.
- This increase is non-monotonic for smaller cyclacenes due to cryptoannulenic effects and strain.
- The dimerization energy for [20]-cyclacene is calculated as -59.3 kcal/mol.
Conclusions:
- Dimerization is a significant factor in cyclacene stability.
- The study provides insights into the degradation pathways of these novel nanohoop structures.
- Extrapolation suggests a convergence of dimerization energy to -46 kcal/mol for large n.
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