X-ray Studies of Biphenylcyclohexanes in the Solid Crystalline and Liquid Crystalline States

The crystal and molecular structures of two disubstituted biphenylcyclohexanes (BCHs) of the general formula R—C6H10C6H4—C6H4—X were determined (BCH5CN, R: C5H11 X: CN; a = 12.671(3), b = 5.567(1), c = 28.695(5) Å, β = 97.174(4)°, space group P2 1/c. BCH30, R: C3H7, X: H, a = 6.839(2), b = 8.219(2), c = 31.159(8) Å, β = 99.63(1)°, space group P21/c). Crystal data only is given of BCH52, R: C5H11 X: C2H5; a = 17.09(2), b = 6.79(1), c = 37.34(3) Å, space group Pbcn Refinement leads to R = 0.089 (BCH5CN) and R = 0.128 (BCH30) respectively. In both compounds, the molecules form layers in the crystalline state. The dihedral angles between the phenyl rings in the biphenyl unit are 2.4° (BCH5CN) and 23.8° (BCH30) respectively. X-ray examinations of the smectic states, and also of some additional BCH-compounds (BCH50, R: C5H11, X: H; BCH54, R: C5H11, X: C4H9; BCH7CN, R: C7H15, X: CN; BCH5NH2, R: C5H11 X: NH2) give monolayered, crystalline smectic B phases for the nonpolar compounds. The compounds containing the polar cyano-group exhibit partial bilayered structures in the smectic A phase as well as in the nematic phase. The bilayer model is discussed.