THE MOLECULAR AND CRYSTAL-STRUCTURE OF 4-METHOXYBENZYLIDENE-4'-NORMAL-BUTYLANILINE (MBBA) AT - 163-DEGREES-C

The molecular and crystal structure of the classic nematogen 4-methoxybenzylidene-4'-n-butylaniline (MBBA) was determined by X-ray diffraction method at -163-degrees-C (diffractometer Nicolet R3m/V, Mo-radiation, 2256 observable reflections, R = 0.058). The monocrystal of MBBA was grown from the polycrystalline sample in a thin capillary at -163-degrees-C by a new method using miniature zone melting procedure with a focused IR laser beam for producing a local molten zone. The crystals are orthorhombic: a = 14.908(4) angstrom, b = 8.391(3) angstrom, c = 18.411(4) angstrom, Z = 6, space group P 2(1). Three independent molecules in the crystal have slightly different conformations but the geometric parameters are normal. The molecular packing is smectic-like and is characterized by the presence of layers parallel to (001), the thickness of the layer is close to the c axis of the unit cell. The relationship between the different phases of solid MBBA is discussed.