Complete basis set and Gaussian-2 ab initio computational studies of planar Hückel and Möbius aromatic hydrogen clusters
✍ Scribed by Branko S. Jursic
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 159 KB
- Volume
- 69
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
Energies for highly symmetric cyclic hydrogen clusters H with D n nh Ž . Ž . symmetry were evaluated with Gaussian-2 G2 and quadratic complete basis set CBSQ ab initio approaches. The energies were compared with linear hydrogen clusters as well as with their energies of formation from hydrogen and charged hydrogens. To better estimate aromaticity and eliminate ring strain energy, energies of formation for hydrogen clusters of the same ring size but with different electron numbers were compared. In this way, it was confirmed that the planar hydrogen clusters in singlet electronic configurations follow the Huckel aromatic rule, while aromaticity of the planar hydrogen Ž . clusters in an excited state triplet follows the Mobius 4 n aromatic rule. It was also determined that hexagonal H is actually the transition-state structure for hydrogen 6 exchange. The activation barrier for this exchange was estimated to be around 75 kcalrmol.