Picene system

Phenacenes are a family of graphite ribbons , where benzene rings are fused together in an alternating pattern. Phenanthrene is the simplest member of this family and other members include the 22-electron system picene (91), the 26-electron system fulminene (92), and the larger member of this family, the 30-electron [7]phenancene, with seven rings (93). ... 

There are three kinds of superconductors based on acceptor molecules M(dmit)2 (Scheme 15, M = Ni, Pd) [293], picene [294], and Ceo [141-143], Cgo system has the highest Tc for molecular superconductors (Tc = 38 K) followed by the picene one Tc = 18 K) however, those two systems are very unstable chemically (caused partly by very weak electron accepting ability) and decompose immediately at ambient condition. 

Peri-condensed aromatic compounds compounds based on angular condensed aromatic hydrocarbon systems, e.g., phenanthrene, chrysene, picene, etc. 

In addition, the occurrence of picene derivatives as well as similar polynuclear aromatic systems (White, 1983) in the solvent extracts of coal might be cited as evidence for the inclusion of sterane-type materials in the precursor material to coal. This does assume that the skeletal structure remains intact throughout the maturation process and that there has been no degradation or even formation of new skeletal systems. Indeed, the biosynthesis of aromatic compounds is well documented, including the synthesis of aromatic species from nonaromatic precursors (Weiss and Edwards, 1980 Lee et al., 1981). 

In general terms, lignite and anthracite coals appear to contain much lower proportions of the volatile organic componnds (10) than the bituminous coals, although alkaline extraction of lignite (and bituminous coal) will yield organic acids of various types that can be characterized. On the other hand, the hexane-soluble portion of the pyridine extracts that were obtained at 50°C (120°F) from coal (carbon content 83.6% w/w) have been identified as alkylated chrysenes as well as alkylated picenes in addition to a mixture of C2g, C29, and C30 paraffins. There were also indicates of the presence of an alicyclic or methyl-substituted five-ring (cat-condensed) system as well as l,2,5,6-dibenzanthracene(s) (Table 10.1). 

A useful 2ilternative to the Kovats system is the Lee retention index (isotherm2il and temperature dependent), based on the polynuclear aromatic hydrocarbon (PAH) standard compounds naphthalene (/ = 200), phenanthrene (/ = 300), chrysene (/ = 400), and picene or benzo(g,h,i)perylene (/ = 500). Isothermal (and temperature-dependent) Kovats and Lee retention indices for many compounds are tabulated in the NIST Chemistry Web Book (Ref. 8). 

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