title: Tetracyclo(2,7-carbazole)s: Diatropicity and Paratropicity of Inner Regions of Nanohoops.
abstract: Three N-substituted tetracyclo(2,7-carbazole)s were synthesized to investigate the inner regions of nanohoops. One compound has a 5,5-dimethylnonane bridge between two neighboring anti-carbazoles, which can be used as covalently bonded "methane probes". These probes near the ring center are strongly shielded by local ring currents and exhibit a singlet at δ = -2.70 ppm in (1)H NMR. To visualize local and macrocyclic ring currents separately, we drew nucleus-independent chemical shift contour maps of tetracyclo(9-methyl-2,7-carbazole) and [n]cycloparaphenylenes (CPPs). Local ring currents make the interior diatropic, and paratropic regions exist only outside the ring. Macrocyclic ring currents in [5]CPP to [7]CPP generate deshielding cones, which are typical of antiaromatic [4n]annulenes.
authors.affiliation: Institute for Molecular Science , Myodaiji, Okazaki 444-8787, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kuroda
authors.affiliation: Institute for Molecular Science , Myodaiji, Okazaki 444-8787, Japan.
authors.forename: Youichi
authors.initials: Y
authors.lastname: Sakamoto
authors.affiliation: Institute for Molecular Science , Myodaiji, Okazaki 444-8787, Japan.
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji 611-0011, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Kayahara
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji 611-0011, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamago