title: In-plane aromaticity in cycloparaphenylene dications: a magnetic circular dichroism and theoretical study.
abstract: The electronic structures of [8]cycloparaphenylene dication ([8]CPP(2+)) and radical cation ([8]CPP(•+)) have been investigated by magnetic circular dichroism (MCD) spectroscopy, which enabled unambiguous discrimination between previously conflicting assignments of the UV-vis-NIR absorption spectral bands. Molecular orbital and nucleus-independent chemical shift (NICS) analysis revealed that [8]CPP(2+) shows in-plane aromaticity with a (4n + 2) π-electron system (n = 7). This aromaticity appears to be the origin of the unusual stability of the dication. Theoretical calculations further suggested that not only [8]CPP(2+) but also all [n]CPP (n = 5-10) dications and dianions exhibit in-plane aromaticity.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Toriumi
authors.forename: Atsuya
authors.initials: A
authors.lastname: Muranaka
authors.forename: Eiichi
authors.initials: E
authors.lastname: Kayahara
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamago
authors.forename: Masanobu
authors.initials: M
authors.lastname: Uchiyama
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D002942:Circular Dichroism; D060328:Magnetic Phenomena; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D001555:Benzene Derivatives; D002412:Cations