| abstract |
Cpds. of formula (I) and, when basic, their acid addn. salts are new R1-(A1)m-Z1-A-Z2-(A2)n-R2 (I) (R1 and R2 are H, 1-10C alkyl (opt. with 1 or 2 methylene replaced by oxygen), fluoro, chloro, bromo, cyano or OCOR; A1 and A2 are each 1,4-phenylene; 1,4-cyclohexylene; 1,3-dioxan-2,5-diyl; piperidin-1,4-diyl; 1,4-bicyclo(2,2,2) octylene or pyrimidin-2,5-diyl, all opt. substd. by 1-4 fluoro. A is 1,4-cyclohexylene substd. at 1 and/or 4 position by 1-5C (fluoro) alkyl or (fluoro) alkoxy, fluoro, chloro, bromo and/or cyano, and opt. substd. by 1 or 2 additional fluoro, chloro, bromo and/or cyano; Z1 and Z2 are each COO, OCO, CH2CH2, OCH2, CH2O or single bond; m is 1 or 2; n is 0 or 1; R is 1-5C alkyl. When m is 2, the A1 gps. can be same or different). They are made e.g. by reacting R1-(A1)m.Z1.CH2CN with (X1CH2CH2)2CH.Z2.(A2)n.R2 (X1 is halo or reactively esterified hydroxy) to give cpds. with A as 1-cyano-1,4 -cyclohexylene. (I) are useful as components of liq. crystal dielectrics, partic. for displays operating on the twisted cell, guest-host, phase deformation and dynamic scattering principles. They provide phases of strong negative dielectric anisotropy; low threshold and control voltages; very low optical anisotropy and relatively low viscosity. When added to mixts. of positive dielectric anisotropy they provide compsns. in which the contrast is nearly independent of viewing angle. (I) have high chemical, thermal and light stability. |