Chemistry Reference
In-Depth Information
Fig. 6 Molecular structures determined by X-ray crystallography for bifluorenylidene (2), the
2
0
,7
0
-dimethyl-derivative of fluorenylidene-xanthene (5), bianthrone (3), and tetrabenzo[7,7
0
]
fulvalene (8), typical examples for the twisted, folded,
anti
-folded, and
syn
-folded conformations
55.7
in the
anti
-folded
The folding dihedrals are very high with A-B (and C-D)
ΒΌ
form and 62.6
(55.5
) in the
syn
-folded form.
6
7
8
The competition between twisting and folding becomes particularly intense in
the case of fluorenylidene-xanthene (5) and its derivatives, where twisted (t) and
