Open-shell singlet character of cyclacenes and short zigzag nanotubes
Bettinger, Holger F.
Schleyer, Paul von Rague
Houk, Kendall N.
- 化学化工－已发表论文 
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 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.