Hexa triphenylene

Akopova reported liquid crystalline phthalocyanines 116ac (Scheme 63) with eight peripheral crown ethers devoid of alkyl chains [132]. Nonetheless, discotic nematic phases could be observed as derived from miscibility experiments with the discotic nematogen hexa(cyclohexanebenzoyloxy)triphenylene and optical textures. In the case of metal-free 116a, a phase width of 43 K was found. Complexation with Zn(II) (116b) decreased the phase range to 35 K and with... 

In relation to these solid-state measurements, a detailed study,195 both empirical and theoretical, of the effect of disorder on the electronic excited states of a hexa(alkylthio)triphenylene 20 (R = S-alkyl) in the bulk state has been conducted. Small but measurable shifts in the absorption maximum are seen... 

Fig. 6.1.1. Examples of disc-shaped mesogens (a) hexa-n-alkanoates of benzene, (b) hexakis ((4-octylphenyl)ethynyl)benzene, (c) hexa-n-alkanoates of scyllo-inositol, (d) hexa-n-alkanoates of triphenylene and hexa-n-alkoxytripheny-lene, (e) hexa-n-alkyl and alkoxybenzoates of triphenylene,(/) hexa-n-alkanoates of truxene, - (g) bis(3, nonyloxybenzoyl)methanato copper(II), > (/)) octasubstituted metallophthalocyanine. ...

Deuterium NMR spectroscopy of the discotic phase of hexa-n-hexyloxy triphenylene has led to similar conclusions. Spectra of two selectively deuterated isotopic species, one in which all aromatic positions are substituted and the other in which only the a-carbon side chains are substituted, bring out the difference between the order parameters of the cores and the tails. Fig. 6.1.3 gives the quadrupole splittings of the aromatic and the a-aliphatic deuterons versus temperature in the meso-phase region. It is seen that the rigid core is highly ordered, the orientational order parameter s ranging from 0.95 to 0.90, whereas the a-aliphatic chains are in a disordered state. 

The nematic phase (N, ) is exhibited by relatively few compounds examples are hexakis((4-octylphenyl)ethynyl)benzene (fig. 6.1.1(A)) and the hexa-n-alkyl and alkoxybenzoates of triphenylene (fig. 6.1.1(e)). The Nd phase has an orientationally ordered arrangement of the discs with no long-range translational order (fig. 6.1.2(f)). Unlike the usual nematic of rod-like molecules, is optically negative, the director n now representing the preferred axis of orientation of the disc normal. The properties of this phase will be discussed in greater detail in 6.5. A twisted nematic (or cholesteric) phase, with the helical axis normal to the director, has also been identified. ... 

Discotic Uquid crystalline molecules are disc-shaped molecules. Examples are Hexaalkanoyloxy benzenes, hexaalkoxy triphenylenes, bis-(4-n-decylbenzoyl)methanato copper (II), hexa-n-alkanoates of truxene and octa substituted phthalocyanines. ... 

Figure 4. Analogy in the topology of the ring in hexa substituted benzene derivatives and of the central ring in triphenylene, perylene, and coronene. (Only the ff electron structures are shown.)...

H. Monobe, S. Mima, T. Sugino, Y. Shimizu, M. Ukon, Alignment behavior of the discotic nematic phase of 2,3,6,7,10,1 l-hexa(4-n-octyloxybenzoyloxy)triphenylene on polyimide and cetyltrimethylammonium bromide coated substrates. Liq. Cryst. 28, 1253-1258 (2(X)1)... 

T. Perova, S. Tsvetkov, J. Vij, S. Kumar, Observation of the orientational transition in hexa(hexylthio)triphenylene using polarized FTIR study. Mol. Cryst. Liq. Cryst. 351, 95-102 (2000)... 

Figure 23 The discotic arnphiphile 2,3,6,7,10,11 -hexa-(trioxoacetyl) triphenylene (cf. Table 3, polymer 15) Is the repeating unit in a columnar stack stabilized by solvophobic interactions in D2O. The temperature versus volume fraction phase diagram shows single columns occurring in the nematic phase (A/) at volume fraction as low as 0.2. Hexagonal columnar and eventually crystalline phases evolve upon increasing concentration. (From R. Hentschke, P.J.B. Edwards, N. Boden, and R. Bushby. Macromol. Symp. 81 361, 1994. With permission.)...

The phase diagram of the discotic arnphiphile based on triphenylene with polar side chains (2,3,6,7,10,1 l-hexa-(l,4,7-trioxoacetyl) triphenylene in D2O, Table 3, polymer 15) [152,157] is reported in Figure 23. Large columnar stacks formed at a volume fraction v 20% (RT) simultaneously with the isotropic nematic transition. The nematic phase was stable up to v 40%, when... 

RgureS Snapshot of the simulation box at T = 300 K containing a stack of eight monomers (2.3.6,7.10.11-hexa-(1,4,7-trioxaoctyl)-triphenylene) in van der Waals representation surrounded by water molecules in stick representation. The left panel shows a view along the micelle s axis, whereas the right panel shows a side view. Note that due to the application of periodic boundary conditions we model a segment of eight monomers within a virtually infinite micelle. 

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]. 

Rgure 2 (a) Schematic of stacking of discotic liquid crystals from disk, to column, to a hexagonal array of columns, (b) Subunits of the classic discotic liquid crystals of hexa-substituted phthalor anines (1), benzenes (2), and triphenylenes (3). 

Measurement in discotic mesophase of hexa-kis(hexyloxy)triphenylene Measurement in phosphatidyl choline vesicle membranes... 

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