Piccardo Matteo, Soncini Alessandro, Fowler Patrick W, Monaco Guglielmo, Zanasi Riccardo
School of Chemistry, University of Melbourne, Victoria, 3010, Australia.
Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, UK.
Phys Chem Chem Phys. 2020 Mar 11;22(10):5476-5486. doi: 10.1039/c9cp06835j.
The altanisation strategy, devised to design molecules with large and paratropic perimeter circulations, is applied to the family of [n]annulenes to give, altan-[n]annulenes, i.e. [n,5]coronenes. Analytical expressions are obtained for the eigenvalues of the Hückel Hamiltonian for altan-[n]annulenes, and used in conjunction with selection rules derived from the ipsocentric approach to predict patterns of global ring current in these systems. Density-functional calculations performed on seven altan-[n]annulenes, three neutral and four charged, give current-density maps in essential agreement with the predictions obtained at the unperturbed Hückel level. All but one of the systems show patterns with the tropicities expected for isolated annulenes, in line with the altanisation concept. The apparent exception is altan-[11]annulene-, the only singlet system with a well defined open-shell character in the studied set. The key role of open-shell character can be accommodated by appropriate choice of the occupation numbers of the initial Hückel molecular orbitals, where the anion altan-[11]annulene- is considered as an [11]annulene inside the [22]annulene anion.
为设计具有大的同芳香性周边环流的分子而设计的altanisation策略，应用于[n]轮烯家族，得到altan-[n]轮烯，即[n,5]蒄。得到了altan-[n]轮烯的休克尔哈密顿量本征值的解析表达式，并与从本位中心方法导出的选择规则一起用于预测这些体系中的整体环电流模式。对七个altan-[n]轮烯（三个中性和四个带电）进行的密度泛函计算给出的电流密度图与在未受扰动的休克尔水平获得的预测基本一致。除了一个体系外，所有体系都显示出与孤立轮烯预期的旋光性一致的模式，这与altanisation概念相符。明显的例外是altan-[11]轮烯阴离子，它是所研究集合中唯一具有明确开壳特征的单重态体系。通过适当选择初始休克尔分子轨道的占据数，可以体现开壳特征的关键作用，其中阴离子altan-[11]轮烯阴离子被视为[22]轮烯阴离子内的[11]轮烯。
