CRYSTAL AND MOLECULAR-STRUCTURE OF A MESOGENIC COMPOUND WITH A LARGE LATERAL BENZENE RING-CONTAINING SUBSTITUENT

The crystal and molecular structure of the nematic compound 4-nitroben zyl 2,5-bis (4-ethyloxybenzoyloxy)benzoate (NEBB) has been determined at -100 degrees C and at room temperature by X-ray analysis. NEBB crys tallizes in space group <P(1)over bar> with two molecules in a unit ce ll of dimensions (values of the room temperature investigation are giv en in brackets) a = 9.547 (3) [9.643 (2)], b = 12.294 (4) [12.452 (3)] , c = 13.536(5) [13.660 (3)] Angstrom, alpha = 68.67 (3) [68.34 (1)], beta = 75.15 (3) [74.40 (1)], gamma = 70.98 (3) [69.65 (1)]degrees. Th e structure was solved by direct methods and refined on F-2 to R value s of wR2 = 0.107 [0.109] and R1 = 0.043 [0.049], respectively, for 334 7 [2422] observed unique reflections. The phenylene bis(benzoate) basi c core of the NEBB molecule has a non-planar but optimally stretched s hape and the lateral ring-containing substituent is oriented parallel to it. The molecules in the crystalline state are arranged perfectly p arallel to each other with an anti-parallel orientation of the neighbo urs. They form lamellar sheets and a tilted layer structure.