Lemniscular hexaphyrins as examples of aromatic and antiaromatic double-twist Möbius molecules.
Two reported [26] and [28]hexaphyrins are analyzed via measured and computed geometries and NMR-shieldings as examples of respectively 4n + 2 pi-electron aromatic and 4n pi-electron antiaromatic double-twist Möbius ring systems, adopting a lemniscular/figure-eight topology with linking number LK = 2pi. Values of local twist (TW) and nonlocal writhe (WR) derived from the relation Lk = Tw + WR appear relatively insensitive to the aromatic/antiaromatic character. The [26]hexaphyrin may adopt differing solution and solid-state conformations.
Rzepa
Henry S
HS
Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ. h.rzepa@imperial.ac.uk