Truxene core

The truxene core has been shown to be also very efficient to enhance TPA properties (Fig. 30) [149] the cttpa value of Pr5 is 6.4-times higher than that of Pr4, while Pr6 presents a TPA efficiency 15.0-times larger than that of Pr4 (Table 4). It is worth noting that this intramolecular extended tt-conjugation in the octupole Pr5 and the dendrimer Pr6 leads to a two-photon excited fluorescence enhancement of 190% and 135% respectively with respect to that of the monomer Pr4. 

An overcrowded fulvalene derivative 211 based on a truxene core was also prepared by treatment of truxenetrione 212 with fluorenyl lithium and dehydration of the formed alcohol using thionyl chloride (Scheme 6.56) [128]. 

To some extent, the design criteria for discotic mesogens are somewhat simpler than those for their calamitic counterparts. In many cases, it is possible to choose a favorite disk-like molecule, then add 6-8 peripheral alkyl chains to generate a mesomorphic (i.e., hquid-crystalline) material. Thus, phthalocyanines, triphenylenes, truxenes, and many other systems will generate mesogenic (i.e., liquid-crystal-like) materials with appropriate substitution these examples are shown in Fig. 24. Note that it is not necessary for the mesogen to have a planar core. 

Figure 11.1. Molecular cores and chains mentioned in this chapter. Cores a = triphenylene, b — dibenzopyrene, c — hexahelicenetetrone, d = phthalocyanine, e — a-glucose, / = /i-glucose, g = tricycloquinazoline, h — truxene, i and j — phenanthrene, k — pyrene, I = dibenzoperylene, m = dibutyldibenzoperylene, n — metal bis-diphenylpropanedionate. Chains 3-methylalkanoate, 0-alkyllactate, 0-(7-methylalkyl)-glycolate, alkanoate, 3,7-dimethyloctyloxy, alkylthio, alkoxy, 3-methoxy-4-(7-methyl-alkoxy)-benzoate.

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