P-Quaterphenyl

For instance, poly-p-phenylenes in their doped states manifest high electric conductivity (Shacklette et al. 1980). Banerjee et al. (2007) isolated the hexachloroantimonate of 4" -di(tert-butyl)-p-quaterphenyl cation-radical and studied its x-ray crystal structure. In this cation-radical, 0.8 part of spin density falls to the share of the two central phenyl rings, whereas the two terminal phenyl rings bear only 0.2 part of spin density. Consequently, there is some quinoidal stabilization of the cationic charge or polaron, which is responsible for the high conductivity. As it follows from the theoretical consideration by Bredas et al. (1982), the electronic structure of a lithium-doped quaterphenyl anion-radical also differs in a similar quinoidal distortion. With respect to conformational transition, this means less freedom for rotation of the rings in the ion-radicals of quaterphenyl. This effect was also observed for poly-p-phenylene cation-radical (Sun et al. 2007) and anion-radical of quaterphenyl p-quinone whose C—O bonds were screened by o,o-tert-hutyl groups (Nelsen et al. 2007). 

The 3,7-disulfonyl chloride of dibenzothiophene 5,5-dioxide has been isolated from the reaction of biphenyl with chlorosulfonic acid. The reaction proceeds via the 2,4,4 -trisulfonyl chloride of biphenyl. This reaction has now been extended to give sulfonic acid derivatives of 3-phenyl- and 3-biphenylyldibenzothiophene 5,5-dioxide. Treatment of p-terphenyl with oleum or chlorosulfonic acid at 100° yields (141a) (46%), and similarly p-quaterphenyl yields 141b (47%). A later... 

Scheinbaum, M.L (1969) Nitration of p-quaterphenyl. Journal of the Chemical Society D, 1235a. 

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. 

Hwang, S.-W. and Chen, Y. (2001) Synthesis and electrochemical and optical properties of novel poly(aryl ether)s with isolated carbazole and p-quaterphenyl chromophores. Macromolecules, 34, 2981-6. 

Figure 98 Temperature dependence of TOF-measured hole and electron mobilities in polycrystalline films of p-terphenyl (a) and p-quaterphenyl (b). The sample thicknesses have been chosen from the range 12-18 pm. The values of the activation energy are given above each of the Arrhenius plots. After Ref. 430.

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. 

In this contribution I will exemplify the power of TDS on some model systems p-quaterphenyl (p-4P) on Au(lll) and p-hexaphenyl (p-6P) on Au(lll), mica(OOOl) and KCl(OOl). I will particularly show that the chemical composition (carbon contamination) and the morphology (surface roughening by sputtering) of the substrate surface can have a tremendous effect on the thin film growth. 

While in p-quaterphenyl the nematic phase is only metastable, p-quinquephenyl and p-sexiphenyl, and probaHy also p-heptiphenyl, have stable nematic phases Beyond p-quinquephenyl smectic phases are expected and proven for p-sexiphenyl. The magnitudes of the transition entropies corr ond to the general observations on liquid crystals... 

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... 

VI. Crystal ructuie of the low-temperature ordered phase of p-quaterphenyl at 110 K. Acta. Cryst. B34 625... 

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

The unexpected isolation of tetraphenylene 1 was claimed in 1928 However, careful determination of the molecular formula by elemental analysis revealed that this sample was actually p-quaterphenyl 2... 

In contrast to this the mechanism of the homolytic substitution of aromatic compounds is by no means clear. This can be demonstrated by two examples. In Walling s book Free Radicals in Solution published in 1957, three different mechanisms for the phenylation of benzene by benzoyl peroxide are discussed (pages 482-487), no definite differentiation based on direct experimental evidence being possible at that time. On the other hand, it was only in 1958, that new products in addition to biphenyl were identified for the decomposition of benzoyl peroxide in benzene solution when DeTar and Long (1958) isolated l, 4, l ,4"-tetrahydro-p-quaterphenyl (8) and 1,4-dihydrobiphenyl (9). 

Table 14.7 Transition energy X (in eV), oscillator strength (in parentheses), collectivity number K, excitation distribution La, CT numbers for the intra-fragment (/a) interactions and CT, , (in %) in the lowest transitions of p-quaterphenyl...

Figure 22. SFC investigations of some selected polyphenyls log k[ of benzene (1), biphenyl (2), p-terphenyl (3), and p-quaterphenyl (4) at 310 K as a function of pressure p (a), density p (b), and log (p/p°) (c) on Nucleosil 100-5 Cig = capacity ratio p° = reference density, here 1 g cm see text according to Kautz [40]).

Figure 4-11. Raman spectra of p-oligophenyls in solid, (a) p-Terphenyl (PP3) (b) p-quaterphenyl (PP4) ...

Figure 4-14. Resonance Raman spectra of the radical anions of >-oligophenyls in THF solutions, (a) p-Terphenyl (b) p-quaterphenyl (c) />-quinquephenyl (d) p-sexiphenyl. Excitation wavelengths are 488.0 and 514.5 nm for (a) and (b-d), respectively. The bands of the solvent are subtracted [70].

Likewise, naphthalene derivatives, fluorene, and fluorenone, as well as 4,4 -substituted p-quaterphenyl, display liquid crystal properties. Moreover, mesophases have been observed in unsubstituted p-quinque-, p-sexti-, and p-septiphenyl. 

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