| abstract |
New compounds of formula (I) have been developed, in which R represents R1, R1O or R1COO, in which R1 represents alkyl containing 1 to 12 C, n and m represent 0 or 1 provided that (n + m) represents 0 or 1; a, b, c and d each independently represent 0 or 1, provided that (a + b + c + d) is different from zero, but excluding the case where a and b represent 0 and m represents 0 and that c or d represents 0. The new compounds are useful constituents of nematic liquid crystal materials. |