Cyclo-oligomerization of 6,12-Diethynyl Indeno[1,2‑<i>b</i>]fluorenes via Diradical Intermediates
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Abstract
Indeno[1,2-<i>b</i>]fluorene derivatives with trimethylsilylethynyl
substituents at the 6- and 12-positions were found to undergo cyclo-dimerization,
cyclo-trimerization, and higher oligomerizations at room temperature.
The cyclic dimer features a novel double-decker motif, composed of
two face-to-face stacked bis(propadienylide)dihydroindeno[1,2-<i>b</i>]fluorenes with a short centroid-to-centroid distance
of 3.50 Å. The existence of a cyclic trimer and higher oligomers
was confirmed by mass spectroscopy and gel permeation chromatography.
The results clearly demonstrate the diradical feature of the indeno[1,2-<i>b</i>]fluorene moiety