Issue 10, 2020

Design of annulene-within-an-annulene systems by the altanisation approach. A study of altan-[n]annulenes

Abstract

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.

Graphical abstract: Design of annulene-within-an-annulene systems by the altanisation approach. A study of altan-[n]annulenes

Article information

Article type
Paper
Submitted
19 Dec 2019
Accepted
04 Feb 2020
First published
18 Feb 2020

Phys. Chem. Chem. Phys., 2020,22, 5476-5486

Design of annulene-within-an-annulene systems by the altanisation approach. A study of altan-[n]annulenes

M. Piccardo, A. Soncini, P. W. Fowler, G. Monaco and R. Zanasi, Phys. Chem. Chem. Phys., 2020, 22, 5476 DOI: 10.1039/C9CP06835J

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