Liquid crystals comprising cyclopentane groups

A compound having the formula:

• wherein
• R is selected from the group consisting of hydrogen and unsubstituted or substituted alkyl each having 1-12 carbon atoms wherein the substitutions are independently one or more of halogen or CN, wherein one or more —CH2— groups of the alkyl group independently are optionally replaced with —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— or —CH═CH—, provided that heteroatoms are not connected directly, except as permitted in the listed groups;
• A and B are each independently selected from the group consisting of:
• 1,4-cyclohexylene, in which one —CH2— or two not directly linked —CH2— are optionally replaced by —O— or —S—;
• 1,4-cyclohexenylene;
• piperidine-1,4-diyl;
• 1,4-bicyclo[2,2,2]octylene;
• 1,4-phenylene, which is optionally substituted with one or more halogens;
• pyridin-5,2-diyl;
• pyrimidin-5,2-diyl;
• naphthalene-2,6-diyl;
• trans-decahydronaphthalene-2,6-diyl;
• tetrahydronaphthalene-2,6-diyl;
• indanediyl;
• indenediyl;
• phenanthrenediyl;
• and dibenzofurandiyl, each of which groups independently is optionally substituted with one or more halogens and/or one or more X1-X4 substituents;
• Z1 is a single bond or C1-C7 unsubstituted or substituted alkylene, wherein the substitutions are independently one or more of halogen or CN, and wherein one or more of the alkylene groups each independently is optionally replaced by —O—, —S—, —CO—O—, —O—CO—, —O—CO—O—, —CF═CF— or —CH═CH—, provided that heteroatoms are not connected directly to each other except as permitted in the listed groups;
• Z2 and Z3 are each independently selected from the group consisting of:
• a single bond, —(CH2)2—, —(CH2)4—, —CH═CHCH2CH2—, —CH2CH2CH═CH—, —CF2O—, —OCF2—, —CF2CF2—, —CF═CF—, —CH2CF2—, —CF2CH2—, —OCF2CF2O—, —C2H4CF2O—, —CH2CF2OCH2—, —CH2OCF2CH2—, —OCF2C2H4—, —C3H6O—, —OC3H6—, —C2H4OCH2—, —CH2OC2H4—, —CH2O—, —OCH2—, —CH═CH—, —C≡C—, and —COO—;
• provided that when Z1 is —OCH2—, —OC(═O)— or —CH2—CH2—, Z2 or Z3 cannot be —OC(═O)—, —OCH2—, —CH2—CH2—, —OC2H6—, —C4H8—, —C≡C—, or a single bond;
• n is 1, or 2;
• m and K are each independently 0, 1, or 2, and m+K+n≧2;
• each X1, X2, X3, and X4 is independently selected from the group consisting of:
• hydrogen, —F, —Cl, —CF3, —CHF2, —OCF3, —OCF2H and —CN;
• Y is independently selected from the group consisting of:
• hydrogen, —F, —Cl, —CN, —NCS, —OCHF2, —CHF2, —OCF3, —OCF2CF3, —CF3, C1-20 alkyl, C1-20 alkoxy, C1-20 alkenyl, and C1-20 alkenyloxy, wherein the alkyl, alkoxy, alkenyl, and alkenyloxy groups independently are optionally substituted by one or more halogens;
• wherein one or more hydrogen atoms in the compound is optionally replaced with deuterium;
• provided that when R is hydrogen and Y has less than 2 carbon atoms and X3, and X4 are both hydrogen or when R is hydrogen and Y has two or more carbon atoms and Z1 has more than 3 carbon atoms, there must be a fused ring system present in the compound or one of Z2 and Z3 must be selected from the group consisting of:
• —CH═CHCH2CH2—, —CH2CH2CH═CH—, —CF2O—, —OCF2—, —CF2CF2—, —CF═CF—, —CH2CF2—, —CF2CH2—, —OCF2CF2O—, —C2H4CF2O—, —CH2CF2OCH2—, —CH2OCF2CH2—, —OCF2C2H4—, —C3H6O—, —OC3H6—, —C2H4OCH2—, —CH2OC2H4, and —CH═CH—;
• and provided that when R is not hydrogen and Y does not contain a —CF2— group and X3 and X4 are hydrogen, either:
• one of A and B must be selected from the group consisting of:
• 1,4-cyclohexylene, in which one or two not directly linked —CH2— groups are optionally replaced by —O— or —S—;
• pyridin-5,2-diyl;
• pyrimidin-5,2-diyl;
• indanediyl;
• indenediyl;
• phenanthrenediyl, and dibenzofurandiyl;
• or
• one of Z1, Z2 and Z3 must be selected from the group consisting of:
• —(CH2)4—, —CH═CHCH2CH2—, —CH2CH2CH═CH—, —CF2O—, —OCF2—, —CF2CF2—, —CF═CF—, —CH2CF2—, —CF2CH2—, —OCF2CF2O—, —C2H4CF2O—, —CH2CF2OCH2—, —CH2OCF2CH2—, —OCF2C2H4—, —C3H6O—, —OC3H6—, —C2H4OCH2—, —CH2OC2H4—, —CH═CH—, and —C≡C—.