Open-shell singlet character of cyclacenes and short zigzag nanotubes.
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.
Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA. chen@chem.uga.edu
Zhongfang
Z
Chen
De-en
DE
Jiang
Xin
X
Lu
Holger F
HF
Bettinger
Sheng
S
Dai
Paul von Ragué
Pv
Schleyer
Kendall N
KN
Houk