title: Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: a potential tetraradicaloid hydrocarbon.
abstract: A tetramesityl derivative of hitherto unknown tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP), which is a potential tetraradicaloid hydrocarbon, was synthesized. Theoretical calculations based on spin-flip time-dependent density functional theory predict that the closed-shell D2h form of TCPTP is more stable than the open-shell D4h form with its slightly tetraradical character. The tetramesityl derivative (Mes)4 -TCPTP exhibits remarkable antiaromaticity as a result of the peripheral 20-π-electron circuit, which causes an absorption maximum at a long wavelength and a small HOMO-LUMO gap. In solution, (Mes)4 -TCPTP most likely adopts rapidly equilibrating D2h structures that interconvert via the D4h transition state. X-ray crystallographic analysis showed (Mes)4 -TCPTP as an approximate D2h structure.
authors.affiliation: Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan); Present address: Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya (Japan).
authors.forename: Shunpei
authors.initials: S
authors.lastname: Nobusue
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Miyoshi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Shimizu
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisaki
authors.forename: Kotaro
authors.initials: K
authors.lastname: Fukuda
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakano
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tobe
keywords: antiaromaticity; corannulenes; singlet diradical; singlet tetraradical; valence tautomerization