Distyrylbenzene derivatives

A Michaelis-Arbusov rearrangement followed by a Wittig-Horner reaction is involved in preparation of the distyrylbenzene derivative 11.37, as shown in Scheme 11.15. Precautions must be taken in the first stage to minimise formation of the carcinogenic by-product bis(chloromethyl) ether 11.16. The stilbene bis-ester 11.38 can be made by a similar procedure, or alternatively by the reaction of ethyl acrylate with 4,4 -dibromostilbene in the presence of a palladium-based catalyst (Scheme 11.16), a synthesis that yields the required trans form of the brightener. 

Fig. 9 Two photon absorption spectra (from 2PIF measurements) of distyrylbenzene derivatives with various substitution patterns, q.3 data from [80,90] q.4 from [94] q.5 from [95,96]...

The distyrylbenzene derivative (141) is photochemically reactive on irradiation in solution. The solvent of choice is acetonitrile/benzene/water (7 2 1) saturated with ammonia. The reactions encountered with this system are derived from electron transfer initiated by p-dicyanobenzene as the electron accepting sensitizer. This process yields the radical cation (142) of the starting material and also the cyclized radical cation (143). These species are trapped by ammonia to yield the final products (144) and (145) in the yields shown. The naphthyl system [141, R-R = (CH=CH)2] is also reactive and affords the analogous products (146) and (147). A study has examined the photochemically-induced cyclization of tetraenes such as (148) under SET conditions in aqueous acetonitrile solution. A variety of electron accepting sensitizers was used. In the example cited the sensitizer (149) was effective and the cascade cyclization yielded the product (150). 

Distyrylbenzene derivatives (e.g. DTVBi) with a nonplanar structure show blue luminescent and electron-transferring properties with high durability. Bathophenathrene (Bphen) and its derivatives (e.g. BCP) are also used for electron transfer. The compounds in Fig. 14-21 show good electron-transfer properties, but is not very large, so that they do not decrease the barrier for electron injection at the electrode, that is, they do not have an electron injection ability [116]. They work as ETL materials by blocking holes. When they are used as ETLs, other methods such as the introduction of a buffer layer are required. 

Phenanthrenes and related compounds were simply synthesized from styrenes and arenes using Heck-type coupling followed by photoinduced intramolecular cyclization via semi one-pot process. Irradiation of distyrylbenzene derivatives afforded dibenzo[aj]anthracenes. The two enantiomers of 2-hydroxyhexahelicene was separated using (5)-(—)cam-phanoyl chloride as the chiral resolving agent. " ... 

Another important class of electron-transporting emitter is the distyryl-arylenes. These have been explored most extensively by workers at Idemitsu Kosan [31, 32], with the bulk of the published data focusing on a compound designated as DPVBi (see Table 13-2). This class of materials may be considered as small molecule analogs of the PPV polymers, with distyrylbenzene and its derivatives ]33] as prototypical examples. Because of the short conjugation length they tend to be blue emitters. 

In general and as expected, brighteners of relatively small molecular size are most suitable for application by exhaustion. Less volatile compounds of larger molecular size tend to be preferred for pad-thermosol application or for incorporation in the polymer mass. Commercially important for exhaust application are the previously mentioned pyrene derivative 11.22, the naphthalimide 11.23, the bis(benzoxazolyl)ethene 11.35, the bis (benzoxazolyl) thiophene 11.36, the distyrylbenzene 11.37 and the stilbene bis (acrylic ester) derivative 11.38. Products of the 11.35 type show excellent light fastness but only moderate fastness to sublimation. In view of this volatility they can be used in the transfer printing of polyester. 

F. Cacialli, R.H. Friend, W.J. Feast, and P.W. Lovenich, Poly(distyrylbenzene- WocA>sexi(ethylene oxide)), a highly luminescent processible derivative of PPV, Chem. Common., 1778-1779, 2001. 

The ester models, as stated above, were all LC, but two of the ether model compounds, the methoxy- and ethoxy-substituted derivatives, were not, despite the fact that each of these mesogens yielded some liquid-crystallinity in the poly(ether) form. Therefore it seems that the polymers in this system tend to be "more liquid crystalline" than the related small molecules. This hypothesis is supported by the fact that Memeger(H) found liquid crystallinity in allhydrocarbon polymers incorporating the distyrylbenzene mesogen, even in cases where the cis/trans ratio of the unsaturations was as large as 0.3, while Campbell and McDonald (10) noted that iodine isomerization to the all-trans form was essential for the observation of an LC phase in the small-molecule derivatives which they prepared. 

Arient, J., Symmetrical and unsymmetrical derivatives of distyrylbenzene. Collect. Czech. Chem. Commun., 46, 101, 1981. 

Both decks of the [2.2]paracyclophane derivatives 160 and 161 could be transformed into 1,4-distyrylbenzene chromophores via the palladium-catalyzed coupling (Heck reaction) with styrene and substituted styrenes adopting the protocol of Jeffery [106]. The fourfold coupling products 162 and 163 were thus obtained with yields up to 70% [107a]. As four new carbon-carbon bonds are formed in this transformation, each single coupling step must proceed with excellent yield. All these reactions lead stereoselectively to products with (E)-configurated double bonds. 

The (Z)-stilbene (6) does not form a rotaxane with dibenzo-24-crown-8 but, when the stilbene is isomerized (sensitized by benzil) to the E form, a pseudo-rotaxane is formed.Lewis and Crompton have reported that the photoacidity of the stilbene derivatives (7) and (8) is dependent on the position of the hydroxy group on the stilbene, and as a consequence the meta derivative undergoes isomerism.The influence of the nitrogen atoms on the photochemistry of the 1,4-distyrylbenzene analogue (9) and related compounds has been assessed. The photophysics and conformational analysis of the stilbene dimer (10) have been studied. Modelling of the optical properties of the stilbenophane (11) has been reported. 

Within the class of oligomeric or low-molecular-weight organic semiconductors distyrylbenzenes (DSBs)—oligomers of poly(p-phenylene vinylene) or PPV and their derivatives enjoy a great deal of interest as new materials for opto-electronic applications such as organic light-... 

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