One of the primary demands for the development of organic light emitting diodes (OLEDs) is the searc — Organic Chemistry Chemistry Question

One of the primary demands for the development of organic light emitting diodes (OLEDs) is the search for highly efficient luminescent materials which can be either small molecules or polymers. For example, fluorene, a methylene–bridged biphenyl, exhibits a higher quantum yield of fluorescence than biphenyl.

Fluorene Biphenyl
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Many fluorene derivatives have been developed that have subsequently found promising applications in flat–panel–display technology. In order to avoid intermolecular interactions, bulky substituents have been introduced at the C₉ position of fluorene. One example of this is compound C, an interesting and useful building block in the development of a highly efficient blue light emitting material, the synthesis of which is shown in the following scheme.

[VISUAL]

Liquid crystals have become a part of our daily life, from wristwatches, pocket calculators, to full color flat–panel displays. Liquid crystal molecules usually contain a rigid core with a flexible terminal alkyl chain as shown in the example below.

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Biphenyl and terphenyl are common basic skeletons for the rigid core of liquid crystals. This kind of structure can be effectively synthesized through palladium catalyzed coupling of an aryl bromide or iodide with arylboronic acid, known as the Suzuki coupling reaction.

Terphenyl
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A typical example of a Suzuki coupling reaction is shown below. Bromobenzene reacts with phenylboronic acid in the presence of a palladium catalyst to give biphenyl.

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The following is a synthetic scheme for the preparation of two liquid crystal molecules, 4–cyano–4’–pentylbiphenyl and G.

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