Synthesis, aromatization and cavitates of an oxanorbornene-fused dibenzo[,]tetracene nanobox

Oxanorbornene-fused double-stranded macrocycles, represented by kohnkene, are not only synthetic precursors toward short segments of zigzag carbon nanotubes but also typical cavitands processing an intrinsic cavity. However, their capability to bind guest molecules in solution remained unexplored. Herein we report a new member of oxanorbornene-fused double-stranded macrocycles, which is named a nanobox herein because of its shape. Reductive aromatization of this oxanorbornene-fused nanobox leads to observation of a new zigzag carbon nanobelt by high resolution mass spectroscopy. The fluorescence titration and NMR experiments indicate that this nanobox encapsulates C 70 in solution with a binding constant of (3.2 ± 0.1) × 10 6 M −1 in toluene and a high selectivity against C 60 and its derivatives. As found from the X-ray crystallographic analysis, this nanobox changes the shape of its cross-section from a rhombus to nearly a square upon accommodating C 60 . A new oxanorbornene-fused nanobox encapsulated C 70 selectively in solution with a binding constant of (3.2 ± 0.1) × 10 6 M −1 . Reductive aromatization of this nanobox led to observation of a new zigzag carbon nanobelt by mass spectroscopy.