Terphenyl and Quaterphenyl

Biphenyl, terphenyl, and quaterphenyl all have room-temperature structures that behave similarly, and also all have low-temperature phases in which only one conformer is present. The torsion angle about the central C-C bond in biphenyl is estimated to be about 10° in the low-temperature form, which is appreciably less than that in the gas phase. In the case of terphenyl, it has been established (41) that the room-temperature structure is disordered each molecule librates in a double-well potential, with the barrier height being about 0.6 kcal/ mol. In the low-temperature form the molecule is stabilized in one of the two minima of the well, and has its terminal rings rotated in the same sense, so that the molecule conserves its center of symmetry. This alternation of rotations between adjacent rings is found (42) also in the low-temperature form of quaterphenyl and results in the molecule being noncentric (even though the crystal structure has a center of symmetry). 

Although many hydrocarbons exhibit fluorescence, often they are colourless and the fluorescence is only just into the blue, e.g. the linear terphenyl and quaterphenyl. Polycyclic ring systems such as terrylene and rubicene are used in analytical methods and OLEDs but a large number are ruled out of commercial use because of their potential to act as carcinogens. However, as mentioned in section 3.5.1.3, pery-lene is a useful fluorophore in a variety of outlets and pyrene is another polycyclic compound of interest. One derivative of pyrene (3.27) is a yellow-green fluorescent dye used in textile applications (Cl Solvent Green 7) and in analysis and sensors (see section 3.5.6.4). 

Decomposition of Aromatic Acyl Peroxides. The decomposition of aromatic acyl peroxides in liquid aromatic compounds is similar to the decomposition of nitrosoacetylarylamines and appears to involve the intermediate formation of free radicals. When dibenzoyl peroxide is heated in benzene, biphenyl, benzoic acid, and small amounts of phenyl benzoate, p-terphenyl, and quaterphenyl are produced. 4 That the second component enters into the reaction is shown by the formation of 4-chlorobiphenyl from the decomposition of di-p-chlorobenzoyl peroxide in benzene 84 and of dibenzoyl peroxide in-chlorobenzene 86... 

The shock against benzene produced H2, light alkanes from Ci to C3, light alkenes from C2 to C3, C2H2, and aromatic hydrocarbons witli molecular weights ranging from 102 (phenylacetylene) to 306 (quaterphenyl). Tliis reaction produced H2, CH4, polyphenyl compounds such as biphenyl, terphenyl, and quaterphenyl. Otlier major products were naphthalene, fluorene, trans-stilbene, phe-nanthrene, isomers of phenylnaphthalene and chrysene. The shock produced ethenyl in greater abundance than etliyl derivatives. 

One of the side reactions is the formation of linear polyaryls, which may be considered to be formed by further reaction of the biaryl initially produced. From the high-boiling residue remaining after the removal of the biphenyl, formed from diazotized aniline, benzene, and alkali, p-terphenyl and quaterphenyl > have been isolated and in the mixture formed in the preparation of 4-methylbiphenyl a hydrocarbon was found... 

Employing the experimental value I = 9.25 eV for benzene in (16), we can fix the value of AZ , which turns out to be AZ = 0.04. The physical interpretation of this value will be discussed in the following section. Since polyphenyls are comprised of benzene rings, a value of AZ, for a molecule is the appropriate fraction of the value for benzene for example, in the case of biphenyl, we take AZ, = 0.02 (just half of AZ = 0.04) for benzene, because for the biphenyl the effect is spread over two benzene rings. In a similar way, AZ = 0.04/3 and 0.04/4 are taken for terphenyl and quaterphenyl, respectively. ... 

Suitable terminal group substitution produces mesomorphic materials with biphenyl, terphenyl and quaterphenyl as cores. Table 3 presents some examples. It is interest-... 

Hexa(oligophenyl)benzenes (e. g. 31 or 33) present one possible approach to the realization of this aim. Two efficient synthetic routes have been elaborated for the preparation of hexa(terphenyl)- and hexa(quaterphenyl)benzene. The first, involving palladium-catalyzed trimerization of diarylacetylenes [54] as the key step, was demonstrated by the synthesis of a hexakis-alkylated hexa(terphenyl)benzene derivative 31 from the corresponding bis(terphenyl) acetylene (32). The peripheral tert-alkyl substituents serve to solubilize the molecule. 

Saitoh, H., Saito, K., Yamamura, Y., Matsuyama, H., Kikuchi, K., Iyoda, M. and Ikemoto, I. (1993) Crystal structures of the room-temperature phase of 4,4"-difluoro-p-terphenyl and 4,4" -difluoro-p-quaterphenyl. Bulletin of the Chemical Society of Japan, 66, 2847-53. 

Mycielski and Lipinski (1978), Kania et al. (1979), Mycielski et al. (1983), and Bak et al. (1995) reported electron and hole mobilities of vapor-deposited polyciystalline layers of various hydrocarbons CuPc, coronene, / -terphenyl, p-quaterphenyl, and tetracene. The mobilities were in the range of 10-3 to 10 5 cm2/Vs and inversely proportional to the field. A mobility with an E-l field dependence is equivalent to a field-independent drift velocity. 

The skeletal configuration of polyphenyl molecules, that is, biphenyl, para-terphenyl, pora-quaterphenyl, and me/a-terphenyl, and the numbering of atoms in those molecules are shown in Fig. 1. In our previous papers we calculated the mobile bond orders and discussed the related phenomena for... 

The construction of symmetry orbitals makes use of the high symmetry of the polyphenyls. These symmetry orbitals are bases of the irreducible representations of the symmetry group. Group theory considerations simplify the problem considerably. Since biphenyl, pttra-terphenyl, and para-quaterphenyl molecules have a Da , symmetry, symmetry orbitals of these molecules will transform as irreducible representations of big, and... 

The calculated ionization potentials and electron affinities of the biphenyl, //ura-terphenyl, parc-quaterphenyl, and meta-terphenyl molecules are shown in Table I, where they are compared with the values from other approaches and with the available experimental values. As shown in Table I, the present calculations yield the most satisfactory results. However, since some of the experimental values are not available in the literature, we cannot compare our results conclusively with the experimental values. 

Wasicki J, Radomska M, Radomski R (1982) Heat capacity of diphenyl, p-terphenyl and p-quaterphenyl from 180 K to their melting points. J. Thermal Analysis 25 509... 

Bottom BA, Prasad, PN (1978) Phase transitions in pdyphenyls Raman spectra ofp-terphenyl and p-quaterphenyl in the solid state. Chem. Phys. 35 331... 

Thermal analysis of polyphenylene, and of benzene, biphenyl, / -terphenyl, and p-quaterphenyl as models, showed that the polymer contained approximately 2 % of defective structures and that these determined the temperature at which thermo-oxidation began. 

The use of monomers having additional p-phenylene rings, i.e. terphenyl or quaterphenyl derived, leads to polymers with increased rigidity and increased degree of crystallinity. TTius, terphenyl diol (11) was condensed with a number of dihalobenzenoid compounds. ... 

Table 3. Unit cell parameters of terphenyl(TP) and quaterphenyl (QP) and of their cation-radical salts (TP)2(SbF.)(CH2C1 ) and (QP)2 (SbF ) (CH Cl ) accoraing to v. Enkelmann...

The electronic absorption spectra of unsubstituted and substituted p-oligophenyls have been reported [66-68]. Each oligomer shows an intense absorption in the ultraviolet region. The band is assigned to the iT-ir transition. The absorption maxima of biphenyl, p-terphenyl, p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl are listed in Table V. The electronic absorption spectra of p-oligophenyls in the radical-anion and dianion states have been studied [68-75]. Furukawa et al. [73] showed that neutral terphenyl is stepwise reduced to its radical anion and dianion in tetahydro-furan by using sodium (Na). In these reduction processes, the reactions... 

Although the correlation is very good, a plot of the data for the homologous series benzene, biphenyl, p-terphenyl, and p,p -quaterphenyl shows the values for the terphenyl to be ca. 9 kJ/mol too low compared to the essentially straight line upon which the other values lie. This conclusion is corroborated by the results from eq 32 involving various combinations of benzene, biphenyl, and p,p -quaterphenyl where the average of the enthalpies of reaction is +17.5 1.5 kJ/mol while the enthalpies of reaction incorporating... 

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