Columnar rectangular

The discotic mesophases are classified in two types columnar, and nematic discotic. The structure of the nematic discotic mesophase (Np, Figure 8.3, left) is similar to that of rod-like molecules, but constituted by disk-like units. In columnar mesophases, the molecules are stacked in a columnar disposition and, depending on the type of columnar arrangement, several columnar mesophases are known. The most common lattices of the columnar phases are nematic discotic (No), columnar nematic (Ncoi), columnar hexagonal (Coin), and columnar rectangular (Col,) mesophases. 

Note 1 See Figs 15a-c for illustrations of molecular arrangements in columnar rectangular mesophases. 

Note 4 There also exist chiral columnar rectangular mesophases, with the molecular discs tilted periodically in the columns and with the tilt directions changing regularly down the columns. 

Fig. 15. Plan views of the two-dimensional lattice of the columns in columnar rectangular (a) to (c) and oblique (d) mesophases. Ovals indicate the planes of the molecular discs.

By reduction of 93 [106] with BH3-THF, Lattermann was able to obtain tridentate [9]-N3 derivative 100 [113] (Scheme 49). While the host system 100 is only crystalline, complexation with Ni(N03)2 induced a columnar rectangular phase as confirmed by X-ray scattering experiments. 

Complexation of 100 with carbonyl complexes of chromium, molybdenum, and tungsten yielded liquid crystalline complexes lOla-c [114] (Scheme 50). All derivatives 101 melted at similar temperatures into the columnar rectangular mesophase (deduced from WAXS and SAXS measurements). However, the clearing points were strongly dependent on the metal center and increased with increasing atom number. Upon complexation, the aza crown macrocycle loses its flexibility, with the metal carbonyl fragment located above the crown leading to a cone-shaped... 

Compound 114d possesses significantly lower transition temperatures (Scheme 60) due to the branched side chains [126]. A columnar phase is present even below room temperature. At 14 °C, anew chiral columnar phase was observed while above 111 °C, an achiral columnar rectangular phase was observed. The spiral-pattern texture of 114d in the chiral Col mesophase is shown in Fig. 17. 

Fig. 4.1 Typical LC phases, a nematic (N), b smecitc A (SmA), c smectic C (SmC), d discotic nematic, e columnar nematic, f columnar hexagnal (Colji), g columnar rectangular (Coir), h columnar oblique (Colob)...

FIGURE 3.1 Schematic representations of commonly observed discotic liquid crystalline phases. Discotic nematic (a) columnar nematic (b) columnar hexagonal (c) columnar rectangular (d). 

Figure 3 Schematic showing (a) nematic phase of disklike mesogens (b) stacking of disklike molecules into columns (c) top view of the columnar hexagonal (Colh) phase (d) top view of one type of columnar rectangular (Cok) phase where the ellipses represent disks that are tilted within the column.

Figure 4. Schematic phase diagrams of members of the radial hexayne series 1,2, and 3 as electron donors with TNF as the electron acceptor [26] Cr crystalline, Nd nematic discotic, Col, columnar rectangular, and Col), columnar hexagonal mesophase (o intracolumnar ordered). Iso isotropic liquid (see footnote 1 in Sec. 3 commenting on the nomenclature of columnar mesophases).

Figure 8. Model of the mesomorphic self-organization of 2,3,4-t isdodecyloxy-benzaldehyde-2 4 -dinit ophe-nylhydrazone in its columnar rectangular mesophase [20] Don donor part, Acc acceptor part.

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