Geometries not within 20 kJ mol -1 of the global minima were discarded, and those within this limit were overlaid (Figure for 4 and 2b for 5). This gives a more realistic picture of the likely gross shape of the terminal group than afforded by a single conformer, and the volume occupied by the terminal group is larger than that of the biphenyl core unit; hence, the molecules are more conical than rod like (Figure ). The layer spacing of 5 is significantly larger than materials with linear terminal chains; we propose that the steric bulk of the cyclic group suppresses the interpenetration of the terminal alkyl chains into adjacent layers and leads to the enhanced layer spacing (Figure , 2d). The observed increases in transition temperatures in compounds 1 -5 can be considered as resulting from the better filling of free volume by materials with bulky end groups than linear chains due to the conical, rather than rod-like, shape. Indeed, in the crystalline state (Figure We next studied the effect of the length of the methylene spacer between the cyanobiphenyl 'core' and the cyclic end-group upon the liquid crystalline properties (Table ). We employed a cyclohexyl terminal group as this not only gave the highest clearing points ( Transition temperatures (T, °C) and associated enthalpies of transition (ΔH, kJ mol -1 ) of cyclohexyl-terminated nOCB compounds.