Columnar liquid crystals phthalocyanines

The Phthalocyanine discogens (Scheme 2) have been extensively studied and their synthesis and properties are well documented in books and articles [20, 21] and references therein. These, together with the poqthy-rins and metal-porphyrins form phases which typify narrow band-gap columnar liquid crystals [21-24]. 

Discotic liquid crystals are a prototypical self-assembled columnar system [9-13]. This class of liquid-crystalline compounds is relatively new, discovered in 1977 by Chandrasekar and coworkers [14,15]. The assembly motif, shown in Figure 2, for this class of compounds has an aromatic core that is surrounded by hydrocarbon chains. These disk-shaped molecules then stack to form columns. These one-dimensional stacks aggregate to form arrayed columns. When the columns have a circular cross-section they typically stack into a hexagonal arrangement as shown in Figure 2(a). Some of the original discotics were hexa-substituted phthalocyanines (1), benzenes (2), and triphenylenes (3), shown in Figme 2(b). The self-assembly of classical discotics will not be presented in depth here because it has been a focus of several comprehensive reviews [9-15]. 

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