Tetracene oligoacenes

Figure 25.1 Selected organic molecules discussed in the course of this chapter. Special attention is drawn to tetracene and diindenoperylene both representing different classes of PAHs, viz. oligoacenes and perylene-derivatives, which are of great interest for organic electronic applications.

As a representative example of the class of oligoacenes, tetracene crystals were grown by sublimation imder streaming H2 gas at a flow rate of 50 seem. The... 

Fig. 2. Surface energies within the vdWDF for the oligoacene (nA), oligophenylene (nP), and the oligothiophene (nT) series. Values for the (100), (010), (001), and (110) planes are given and the corresponding surface terminations are depicted for tetracene (4A).

FIGURE 3.1.2 Chemical structure of anthracene- and tetracene-based oligoacenes. 

A showcase in organic molecules, on the other hand, are polycyclic aromatic hydrocarbons (PAH). Malloci and co-workers have investigated the five smallest oligoacenes (naphthalene, anthracene, tetracene, pentacene, hexacene), which are depicted schematically in Fig. 8. PAHs have a conjugated ji-electron system and are a relevant class of materials in chemistry, materials science, and especially astrophysics. Acenes are a... 

Fig. 8 Schematic representation of the geometries of the first five oligoacenes. From top to bottom naphthalene, anthracene, tetracene, pentacene, and hexacene. Reprinted from ref 56. Copyright 2007, with permission from Elsevier. 

The Diels-Alder reaction ([4+2] cycloaddition) [8] provides one of the most powerful methods for the constmc-tion of PAHs because it affords one-step formation of the six-membered ring framework, the basic unit of these derivatives. This chapter, based on the results of our work, will highUght the synthesis of substituted oligoacenes including anthracene (1), tetracene (2), and pentacene (3) cores by Diels-Alder reactions using arynes and quinones as dienophile components and furans, thiophene-1,1-dioxides, and o-quinodimethane as diene components. The synthetic methodology will be accompanied by discussions on molecular and packing stmctures as weU as solid-state optical properties. 

SCHEME 14.1 The oligoacene members anthracene (1), tetracene (2), and pentacene (3). 

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