From Fenestrindane towards Saddle-Shaped Nanographenes Bearing a Tetracoordinate Carbon Atom

Two saddle-shaped polycyclic aromatic compounds (8a and 8b) bearing an all-cis-[5.5.5.5]fenestrane core surrounded by an o,p,o,p,o,p,o,p-cyclooctaphenylene belt were synthesized and characterized by NMR spectroscopy and mass spectrometry. The key step of this synthesis involves the formation of four cycloheptatriene rings from the corresponding electron-rich 1,4,9,12-tetraarylfenestrindane derivatives 7a and 7b in Scholl-type cyclizations. The structural details of the D-2d-symmetric saddle compound 8a were determined by X-ray crystallography, and the properties of 8a and 8b were studied by UV/Vis and fluorescence spectroscopy and cyclic voltammetry.