Пентацен: Бес сақиналы полициклдік көмірсутек

Hydrocarbon compound (C22H14) made of 5 fused benzene rings

Pentacene (|C22H14) is a polycyclic aromatic hydrocarbon consisting of five linearly fused benzene (|C6H6) rings. This highly conjugated compound is an organic semiconductor. The compound generates excitons upon absorption of ultra violet (UV) or visible light; this makes it very sensitive to oxidation. For this reason, this compound, which is a purple powder, slowly degrades upon exposure to air and light. Structurally, pentacene is one of the linear acenes, the previous one being tetracene (four fused benzene rings) and the next one being hexacene (six fused benzene rings). In August 2009, a group of researchers from IBM published experimental results of imaging a single molecule of pentacene using an atomic force microscope. In July 2011, they used a modification of scanning tunneling microscopy to experimentally determine the shapes of the highest occupied and lowest unoccupied molecular orbitals. In 2012, pentacene doped p terphenyl was shown to be effective as the amplifier medium for a room temperature maser.

Oligomers and polymers based on pentacene have been explored both synthetically as well as in device application settings. Polymer light emitting diodes (PLEDs) have been constructed using conjugated copolymers (1a–b) containing fluorene and pentacene. A few other conjugated pentacene polymers (2a–b and 3) have been realized based on Sonogashira and Suzuki coupling reactions of a dibromopentacene monomer. Non conjugated pentacene based polymers have been synthesized via esterification of a pentacene diol monomer with bis acid chlorides to form polymers 4a–b. Various synthetic strategies have been employed to form conjugated oligomers of pentacene 5a–c including a one pot four bond forming procedure which provided a solution processable conjugated pentacene dimer (5c) which exhibited photoconductive gain >10, placing its performance within the same order of magnitude as thermally evaporated films of non functionalized pentacene which exhibited photoconductive gain >16 using analogous measurement techniques. A modular synthetic method to conjugated pentacene di , tri and tetramers (6–8) has been reported which is based on homo and cross coupling reactions of robust dehydropentacene intermediates. Non conjugated oligomers 9–10 based on pentacene have been synthesized,

Pentacenes have been examined as potential dichroic dyes. The pentacenoquinone displayed below is fluorescent and when mixed with liquid crystal E7 mixture a dichroic ratio of 8 is reached. Longer acenes align better in the nematic liquid crystal phase. Combined with buckminsterfullerene, pentacene is used in the development of organic photovoltaic prototypes. Organic photovoltaic cells are cheaper and more flexible than traditional inorganic cells, which could potentially open doors to solar cells in new markets. Pentacene is a popular choice for research on organic thin film transistors and OFETs, being one of the most thoroughly investigated conjugated organic molecules with a high application potential due to a hole mobility in OFETs of up to 5.5 cm2/(V·s), which exceeds that of amorphous silicon. Pentacene, as well as other organic conductors, is subject to rapid oxidation in air, which precludes commercialization. If the pentacene is preoxidized, the pentacene quinone is a potential gate insulator, then the mobility can approach that of rubrene – the highest mobility organic semiconductor – namely, 40 cm2/(V·s). This pentacene oxidation technique is akin to the silicon oxidation used in the silicon electronics.