Cyanobiphenyls

Figure Bl.19.8. (a) STM image (5.7 mu x 5.7 mu) of 10-alkylcyanobiphenyl on graphite (b) model showing the packing of the molecules. The shaded and unshaded segments represent the alkyl tails and the cyanobiphenyl head groups, respectively. (Taken from [38], figure 2.)...

C12H21N 773777-37-4) see Dicycloverine 2 -cyanobiphenyl-4-carboxaldehyde (C14Hc.NO 135689-93-9) see Valsartan 7V-[(2 -cyano[l,l -biphenyl]-4-yl)methyl]-L-valine methyl ester... 

C5H7NO2 105-56-6) see Allopurinol Amlexanox Bemegride Ethosuximide Etozolin Folic acid Gabapentin Paroxetine Phensuximide Sulfadimethoxine Theophylline Tinoridinc Trimethoprim Valdetamide Valproic acid ethyl 2-(2 -cyanobiphenyl-4-ylmethylamino)-3-nitroben-zoate... 

C23H19N3O4 136285-67-1) see Candesartan cilexeti ethyl l-(2 -cyanobiphenyl-4-yImethyl)-2-ethoxybenzinii-dazole-7-carboxylate... 

Fig. 4a,b. The effect of substitution of an alkoxy tail for an alkyl tail in cyanobiphenyls a transition sequence is K kf N b transition sequence is K N /... 

Scheme 3. Lowest energy conformations for the mesogen 5CB (4-n-pentyl-4 -cyanobiphenyl)...

The dimer model proposed by Wilson [83] was found not to exhibit a nematic phase but smectic A and B phases and so, although semi-realistic features are included, the model is not able to reproduce the behaviour of real dimers such as the a,co-bis(4 -cyanobiphenyl-4-yloxy) [87], which exhibit nematic phases, although liquid crystal dimers exhibiting smectic phases are also known [88]. In these simulations, the GB-GB interaction appears to be too strong and so the system forms a smectic phase in which the GB and LJ units... 

The first report on the liquid crystalline properties of these compounds was published by Gray and Mosley [44] in 1976. The series of 4 -n-alkyl-4-cyanobiphenyls (CBn) have been widely studied by different methods due to their readily accessible nematic ranges around room temperature. The compounds have the phase sequences crystal-nematic-isotropic for CBS, CBIO, and monotropic nematic for CBS, CB4 crystal-smectic A-nematic-isotropic for CB9 crystal-smectic A-isotropic for CBll. The lower homologous CB2 is nonmesogenic. The general chemical structure of the compounds CBn is presented in Fig. 1. 

Table 2. Crystal and molecular data of mesogenic 4 -n-alkoxy-4-cyanobiphenyls (CBOn)... 

The crystal structure of the mesogenic compound 4 -(4-hydroxy-1-n-butoxy)-4-cyanobiphenyl (CB0(CH2)40H) was described by Gehring et al. [59]. In... 

From the X-ray data of single crystals, it is possible to obtain information about the intermolecular interactions and the overlapping between the polar groups of neighbouring molecules. In Sects. 2.1.1, 2.1.2 and 2.1.3 the crystal structures of cyanobiphenyls were described. No cyano-phenyl overlapping of type 1 can be observed in the solid state of the compounds. 

In some cases a cyano-phenyl overlapping of type II was found in the solid phase of the cyanobiphenyl compounds (Fig. 30). 

D. O., Micro-reactor synthesis synthesis of cyanobiphenyls using a modified Suzuki coupling of an aryl halide and aryl boronic acid, in Ehefeld, W. (Ed.), Microreaction Technology 3rd International Conference on Microreaction Technology, Proc. of... 

There are also some trends when looking at the main chain flexibility. Table II demonstrates that when the main chain flexibility decreases from cyanobiphenyl containing polymethacrylates to polysiloxanes, not only does the Tg drop, but the isotropization temperature increases. However, the trend is the opposite when the mesogen is methoxyphenyl benzoate (18). Therefore, this effect of the main chain flexibility is still ambiguous. 

Liquid-crystalline complexes (metallomesogens) containing platinum(II) are new types of materials that have been the subject of several studies. These have largely included complexes of the type trans-[PtX2L2] (X = C1, L = cyanobiphenyls 229 X = C1, carboxylate, L = 4-alkoxy-4 stilbazoles 230 X = C1, L = 2,4-, 3,4-, or 3,5-dialkoxystilbazoles, 2,3,4-, 2,4,5-, or 3,4,5-trialkoxystilbazoles).231,232 Their liquid-crystalline properties have also been reported. 

Each of these couplings is inversely proportional to the cube of the distance between the atoms concerned, and all the dipolar couplings depend on the degree of orientation of the molecules. The ratios of couplings thus depend on the ratios of distances in the molecule, and from them the entire molecular structure, except for the overall size, may be determined. Studies of silyl compounds dissolved in cyanobiphenyl liquid crystals have yielded the following HSiH angles ... 

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