Phenylenes angular

Unsubstituted Poly(meta-phenylene) is far more soluble than poly(para-phen-ylene) PPP1 of comparable molecular weight due to the angular structure of the meta-derivative. Poly(meta-phenylene) 48 can be prepared using the Yamamoto procedure [20] ca. 35% of the material formed is soluble in toluene. 

In 1993, Scherf and Chmil described the first synthesis of a ladder-type poly(pflra-phenylene-czs-vinylene) (116) [138]. On the one hand, ladder polymer 116 represents, a planar poly(phenylene) containing additional vinylene bridges on the other hand, it is a poly(phenylenevinylene) with aryl-aryl linkages in the polymeric main chain. The target macromolecules, as fully aromatic ladder polymers, are composed of all-carbon six-membered rings in the double-stranded main chain (an example of angularly annelated poly(acene)s). 

Scheme 6.79 Hydrosilylation of ketones [164], Dotz benzannulation chemistry [165], cobalt-mediated synthesis of angular [4]phenylenes [166], and nickel-mediated coupling polymerizations [167],...

The FVP of angular [3]phenylene and bis(2-ethynylphenyl)ethyne has been found to produce benz[g/z]fluoranthene and chrysene,54 respectively. A non-chain stepwise radical mechanism which is initiated by hydrogen-atom transfer from the donor to azulene has been proposed55 for the mechanism of the uncatalysed transfer-... 

The introduction of angular connectors (e.g. 1,3-phenylenes, 2,7-naphthylenes) in the Jt-conjugated backbones may provide an oligomer with a preferred helical... 

Figure 17. Numbering of atoms in biphenylene (a) as well as in linear and angular [3] phenylenes denoted by (b) and (c), respectively.

The picture of the angular [3]phenylene offered by both HF/6-31G model and the X ray structure is just the opposite to that in its linear counterpart the central benzene ring is more localized than in biphenylene, whereas the terminal ones are slightly more delocalized. This is reflected in their Lf,(dcc) indices which are 0.32 and 0.12, respectively. It should be mentioned that the double bond C(4b)-C(4c) bridging two four-membered fragments is the shortest and most localized one, which is compatible with its high average s-character of 41 %. 

The target structures in the final example are fully aromatic polymeric hydrocarbons, consisting of all-carbon six-membered rings - so-called angularly annulated polyacenes 91 [55]. The structural difference between those and the methylene-bridged poly(phenylene)s is the replacement of the benzylic methylene bridges by vinylene moieties. 

The various ID CP NMR spectra of a biaxially drawn industrial PET film are shown in Fig. 14.7. The pronounced sensitivity to the orientation of the sample with respect to the applied magnetic field is also shown [7]. However, the orientation distribution is relatively complicated and, therefore, difficult to quantify from these data. For PET, overlapping resonances from carboxyl and phenylene group carbons are especially troublesome and, consequently, restrict the angular information achievable in ID NMR experiments. 

Fig. 5,11. Order distribution-functions of various parts of a polyacrylate with side-chain mesogen (phenylene-4-hydroxybenzoate) separated by a flexible spacer (hexamethylene). Determined from the angular dependence of the deuterium NMR line-shape. Presented by H. W. Spiess, Dechema Tagung 1987, see also Refs. The angle p is defined between the ma etic field and the...

Their detailed analysis shows that the phenylene group in this polymer undergoes two types of motion simultaneously, both about the C1-C4, axis. The primary motion consists of large-angle jumps between two sites whereas the secondary motion involves restricted rotational diffusion over limited angular amplitude. These motions have been described by an inhomogeneous distribution of correlation times [43]. 

Diercks R, VoUhardt KPC (1986) Novel Synthesis of the Angular [3]Phenylene (Terphe-nylene) by Cobalt-Catalyzed Cydization of Bis(2-ethynylphenyl)ethyne — a Molecule with an Internal Cyclohexatriene Ring. Angew Chem Int Ed Engl 25 266... 

Schmidt—Radde RH, Vollhardt KPC (1992) Total Synthesis of Angular [4]Phenylene and [5]Phenylene. J Am Chem Soc 114 9713... 

Cata-condensed polycyclic hydrocarbons contain benzenoid rings such that each fused carbon atom is common to no more than two rings. The benzenoid rings may be linearly annelated (acenes), as in the series naphthalene (19), anthracene (20), and naph-thacene (21), or they may be angularly annelated, as in phenanthrene (22), benz[a]anthracene (23), benzo[c]phenanthrene (24), chrysene (25), and tri-phenylene (26). Except for some isolated examples... 

Figure 4.2. Simple phenylene topologies (a) linear [4]-, (b) angular [4]-, (c) zigzag [4]-, (d) branched [4]-, (e) (mixed) bent [4]-, and (f) circular [6 phenylene.

Figure 4.3. Phenylenes and topologically related PAHs (a) linear [/VJphenylenes and polyacenes (b) angular/zigzag [/VJphenylenes and polyphenanthrenes/helicenes (c) circular [6]phenylene sheet and graphite (d) archimedene (C120) and fullerene C o).

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