Twisted biphenyl

X-Ray structural analysis of bridged biphenyls containing sulfoxide, and sulfone functions in the bridge, 1,11 -dimcthyl-5,7-dihydrodibenzo[rv ]thiepine. V-oxide 24 and. Y,.Y-dioxide 25 in racemic form, was undertaken <2000HGA479>. The crystals of both 24 and 25 are centrosymmetric (RAY). The crystal structures of 24 and 25 (Table 6) showed similar twisted biphenyl moieties with dihedral angles (9) (C(2)-C(l)-C(8)-C(9) and C(6)-C(l)-C(8)-C(13)) in the range of 62.5-65.0°. 

Research utilizing the thiepine skeleton in material science has been reported. For example, liquid crystals with chiral dihydrodibenzo[c,i ]thiepines were studied. The enantiomerically pure (-)-(i )-3,9-bis[4-(dodecyloxy)benzoyl-oxy]-5,7-dihydro-l,l l-dimethyldibenzoR,f]thiepine 80 and (—)-(R)-3,9-bis[4-(dodecyloxy)benzoyloxy]-5,7-dihydro-1,1 l-dimethyldibenzoR,f]thiepine dioxide 82 display smectic C mesophases by a rigid twisted biphenyl core and axial chirality <1998JOC3895>. 

Next we come to the dihedral groups T> , V h and D d, which are often the trickiest to identify. These all have a C axis with n C2 axes perpendicular to it. The group T>2 has mutually three perpendicular C2 axes and no other symmetry elements. An example is twisted biphenyl (by some angle not equal to 0° or 90°) ... 

The aporphine alkaloids contain a twisted biphenyl system, and can exist either in the absolute configuration (LXXIX S series) or its mirror image (LXXX R series) (61). 

A new class of semiconductors based on a tertiary diamine structure, 5,11-disub-stituted indolo[3,2-/ ]carbazole (15a-15d) (Figure 3.1.5) have been reported.[109,l 10] The derivatives are soluble in organic solvents such as toluene, chloroform, and chlorobenzene. OTFTs using these carbazole derivatives (15a-15d) exhibited p-chan-nel behavior with mobilities of up to 0.12 cm V s and a current on/off ratio of 10 . Recently dichloro derivatives (15e-15f) of these carbazoles gave improved device performance with mobility of 0.14 cm V s . [lll] 2,7-Carbazolevinylene-based conjugated oligomers, 15h-15j, have also been tested in OTFTs.[112,113] The higher mobility of 15h (0.30 cm V s with on/off ratio of 10 ) compared to 15J (10 cm V s with on/off ratio of 10 ) is attributed to the relative coplanar structure of the former and twisted biphenyl units in latter. 

Y. Hu, T. Shimizu, K. Hattori, M. Shiotsuki, F. Sanda, T. Masuda, Synthesis and gas permeation properties of POLY(diarylacetylene) s having substituted and twisted biphenyl moieties, J. Polym. Sci. Part A Polym. Chem. 48 (4) (2010) 861-868. 

The absolute configuration of corilagin (43) has been determined by reference to the twisted biphenyl system of the cyclo-octane lignan schizandrin (44) (Fig. 10). 

Figure 1.7. Axially chiral molecules (a)-(d) and a molecule with a chiral plane (e). (a) Dichlorallen, (b) twisted biphenyl, (c) helicene, (d) highly twisted aromatic compound [25], and (e) paracyclophane.

Y.-H. Kim, H.-S. Kim, S.-K. Ahn, S. O. Jung and S.-K. Kwon. Synthesis of new highly organosoluble polyimides bearing a noncoplanar twisted biphenyl unit containing f-butyl phenyl group. Bull. Korean Chem. Soc. 23, 2002,933-934. 

---