A compound selected from the compounds of the formulae N-1 to N-3 in which R N denotes H, alkyl or alkoxy each having 1 to 12 C atoms, or alkenyl, alkenyloxy or alkoxyalkyl each having 2 to 12 C atoms, in which one or more CH 2 -groups may be replaced by or denotes a group R P, R P denotes halogen, CN, NCS, R F, R F -O- or R F -S-, wherein R F denotes fluorinated alkyl having 1 to 9 C atoms or fluorinated alkenyl having 2 to 9 C atoms, Z N1 and Z N2, identically or differently, denote -CH=CH-, -CF=CF-, -CH=CF-, -CF=CH-, -C≡C-, -C≡C-C≡C- or a single bond, denote a radical selected from the following groups: a) the group consisting of 1,4-phenylene, 1,4-naphthylene and 2,6-naphthylene, in which one or two CH groups may be replaced by N and in which one or more H atoms may be replaced by L, b) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene, bicyclo-[1.1.1]pentane-1,3-diyl, 4,4'-bicyclohexylene, bicyclo[2.2.2]octane-1,4-diyl and spiro[3.3]heptane-2,6-diyl, in which one or more non-adjacent CH 2 groups may be replaced by -O- and/or -S- and in which one or more H atoms may be replaced by F, c) the group consisting of thiophene-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by L, L on each occurrence, identically or differently, denotes F, Cl, CN, SCN, SF 5 or straight-chain or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, Y 1 and Y 2, identically or differently, denote H, F, Cl or CH 3, and t is 0 or 1. R N denotes H, alkyl or alkoxy each having 1 to 12 C atoms, or alkenyl, alkenyloxy or alkoxyalkyl each having 2 to 12 C atoms, in which one or more CH 2 -groups may be replaced by or denotes a group R P, R P denotes halogen, CN, NCS, R F, R F -O- or R F -S-, wherein R F denotes fluorinated alkyl having 1 to 9 C atoms or fluorinated alkenyl having 2 to 9 C atoms, Z N1 and Z N2, identically or differently, denote -CH=CH-, -CF=CF-, -CH=CF-, -CF=CH-, -C≡C-, -C≡C-C≡C- or a single bond, denote a radical selected from the following groups: a) the group consisting of 1,4-phenylene, 1,4-naphthylene and 2,6-naphthylene, in which one or two CH groups may be replaced by N and in which one or more H atoms may be replaced by L, b) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene, bicyclo-[1.1.1]pentane-1,3-diyl, 4,4'-bicyclohexylene, bicyclo[2.2.2]octane-1,4-diyl and spiro[3.3]heptane-2,6-diyl, in which one or more non-adjacent CH 2 groups may be replaced by -O- and/or -S- and in which one or more H atoms may be replaced by F, c) the group consisting of thiophene-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by L, L on each occurrence, identically or differently, denotes F, Cl, CN, SCN, SF 5 or straight-chain or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, a) the group consisting of 1,4-phenylene, 1,4-naphthylene and 2,6-naphthylene, in which one or two CH groups may be replaced by N and in which one or more H atoms may be replaced by L, b) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene, bicyclo-[1.1.1]pentane-1,3-diyl, 4,4'-bicyclohexylene, bicyclo[2.2.2]octane-1,4-diyl and spiro[3.3]heptane-2,6-diyl, in which one or more non-adjacent CH 2 groups may be replaced by -O- and/or -S- and in which one or more H atoms may be replaced by F, c) the group consisting of thiophene-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by L, L on each occurrence, identically or differently, denotes F, Cl, CN, SCN, SF 5 or straight-chain or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, Y 1 and Y 2, identically or differently, denote H, F, Cl or CH 3, and t is 0 or 1.