Investigation of H2 Physisorption on Corannulene (C20H10), Tetraindenocorannulene (C44H18), Pentaindenocorannulene (C50H20)

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• 作者：Pablo A. Denis
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：February 21, 2008
• 年：2008
• 卷：112
• 期：7
• 页码：2791 - 2796
• 全文大小：247K
• 年卷期：v.112,no.7(February 21, 2008)
• ISSN：1932-7455

文摘

The hydrogen storage capacities of the recently synthesized tetraindenocoranulene C₄₄H₁₈ and pentaindenocorannulene C₅₀H₂₀ have been investigated and compared with those of corannulene and C₆₀. The results forthe physisorption of a single H₂ on the concave side indicate that the adsorption energies (E_ads) fortetraindenocorannulene and pentaindenocorannulene are very similar, 2.9 and 3.0 kcal/mol, respectively. Thelater values are slightly larger than that estimated for corannulene, 2.4 kcal/mol, and about half of theencapsulation energy of H₂ in C₆₀, 5.4 kcal/mol. The differences in adsorption energies can be explainedconsidering the dipole moments of the molecules. For C₅₀H₂₀ and C₄₄H₁₈ they are very similar, 4.0 and 3.7Debye. However, it is much smaller in corannulene, 2.0 Debye, which explains the lower E_ads observed forthe later polyarene. The E_ads presents a different behavior on the electron-poor convex side; they are nearlyidentical for all of the molecules considered. The interaction energies on the convex side, determined forcorannulene, tetraindenocorannulene, pentaindenocorannulene, and C₆₀, are 1.2, 1.1, 1.1, and 1.2 kcal/mol,respectively. The hydrogen storage capabilities are discussed in terms of the results obtained for the sandwichcomplexes between pentaindenocorannulene with benzene or corannulene. As a by product, we estimated thecomplexation energies for the benzene-pentaindenocorannulene and corannulene-pentaindenocorannulenepairs as 6.0 and 8.3 kcal/mol, respectively. Finally, we replaced some carbon atoms in corannulene andpentaindenocorannulene with nitrogen atoms. The adsorption energies were increased; C₁₆N₄H₁₀ has nearlythe same adsorption energy as the much larger pentaindenocorannulene. In the case of pentaindenocorannulene,the introduction of six nitrogen atoms (12% of carbon atoms replaced) increases the adsorption energy, about0.2 kcal/mol. The present results showed that the introduction of a small number of nitrogen atoms canincrease the adsorption energy in carbon structures without increasing the weight of the material too much,but the increment seems to be strongly dependent on the position of the nitrogen atoms.