Open-shell singlet character of cyclacenes and short zigzag nanotubes

Zhongfang Chen; De-en Jiang; Xin Lu; Holger F Bettinger; Sheng Dai; Paul von Ragué Schleyer; Kendall N Houk

doi:10.1021/ol7023339

Open-shell singlet character of cyclacenes and short zigzag nanotubes

Org Lett. 2007 Dec 20;9(26):5449-52. doi: 10.1021/ol7023339. Epub 2007 Nov 29.

Authors

Zhongfang Chen¹, De-en Jiang, Xin Lu, Holger F Bettinger, Sheng Dai, Paul von Ragué Schleyer, Kendall N Houk

Affiliation

¹ Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA. chen@chem.uga.edu

PMID: 18044906
DOI: 10.1021/ol7023339

Abstract

The electronic ground states of [n]cyclacenes, as well as short-zigzag nanotubes, computed at unrestricted broken spin-symmetry density functional theory (UBS-DFT), were found to be open-shell singlets, rather than triplets. Computations for [6]cyclacene at complete active space self-consistent field (CASSCF) and multireference perturbation theory (MRMP2) levels support this conclusion. Along with strain, the radical character of the open-shell singlet with antiferromagnetically coupled electron spins may contribute to the difficulties in synthesizing [n]cyclacenes.