Mesogenic properties of single ring compounds:: dipentyl derivatives of p-carboranes and bicyclo[2.2.2] octane

The dipentyl derivatives of 10- and 12-vertex p-carboranes and bicycle [2.2.2] octane have been prepared and studied in the pure state and in binary mixtures with a nematic host. Only 1,4-dipentylbicyclo [2.2.2] octane was found to exhibit a monotropic nematic transition. The extrapolated virtual nematic-isotropic transition temperatures provide the expected order of ring effectiveness in supporting the nematic mesophase: bicycle [2.2.2]octane > 12-vertex p-carborane > 10-vertex p-carborane. The results for the single ring derivatives [1]b were compared with clearing temperatures for the two-ring mesogens [2]c.