Chemistry Reference
In-Depth Information
FIGURE 9.30
Chemical structures of several TPA dendrimers [121-124].
steadily. The maximum
s
2
reaches up to 7000GM for the largest dendrimer. In
such dendrimers, fast energy migration and exciton delocalization are observed,
which can be related to enhanced NLO effect. To ensure the planarity and
therefore electron delocalization around the nitrogen atom, Fang et al. introduced
methylene bridges to constrain the flexibility of the triphenylamine group [122].
As a result, large cross-sections (up to 6100 GM) was obtained for structure
.
Besides pure organic dendrimer, organometallic unit can also be employed. For
example, Humphrey's group reported a Ru-containing organometallic dendrimer
43
42
that showed not only good TPA property but also remarkable three-photon
absorption ability [123]. In a recent report, Burn's group used their bisfluorene-
biphenyl dendrimer (structure
) to realize two-photon pumped lasing, showing
great application potentials in up-conversion lasers [124].
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