Chemistry Reference
In-Depth Information
Scheme 36 Preparation of fully conjugated 11,12-dimesitylindeno[2,1-
a
]fluorene 123b [
89
]
Fig. 15 Eclipsed (
top
) and staggered (
bottom
) crystal morphs of 123b [
89
]
robustness to the bulky mesityl groups adequately shielding the reactive 11- and 12-
positions.
The absorption spectra of 123b showed three distinct
transitions in the
480-540 nm domain (
l
max
: 537 nm) as well as a low energy tail to 730 nm,
affording a 1.70 eV band gap energy. As with the previous mentioned fully
conjugated [1,2-
b
]IFs, no fluorescence was observed for 123b. Cyclic voltammetry
data showed that 123b exhibited both a reversible oxidation and reduction at
1.51
and 0.59 V, respectively.
X-Ray structural data for 123b clearly showed the indeno[2,1-
a
]fluorene
scaffold (Fig.
15
). Interestingly, two independent molecules of 123b were found
where the mesityl groups are in either an eclipsed or staggered fashion (top and
bottom, respectively), exhibiting a torsion angle of 1.7
and 15.2
, respectively.
Examination of the internal bond lengths of 123b revealed the expected alternating
long (1.431 and 1.480
˚
) and short (1.359 and 1.391
˚
) motif, similar to 92a.
