The molecular and crystal structure of 4-methoxybenzylidene-4′-<i>n</i>-butylaniline (MBBA) at −163°C

Abstract

Abstract The molecular and crystal structure of the classic nematogen 4-methoxybenzylidene-4′-n-butylaniline (MBBA) was determined by X-ray diffraction method at −163°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°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)Å, b = 8·391(3)Å, c=18·411(4)Å, Z = 6, space group P 21. 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.