Compounds of the formula I, in which R 1 denotes H, a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, where, in addition, one or more CH 2 groups in these radicals may each be replaced, independently of one another, by -C≡C-, -CH=CH-, - O-, -O -, - - or -O- in such a way that O atoms are not linked directly to one another, R 2 denotes F, Cl, OCF 3, OCHF 2, OCHFCF 3, OCF 2 CHFCF 3, CF 3, CN, SF 5, NCS, NCO, SCN or OCN, A 1, A 2 and A 3 each, independently of one another, identically or differently, denote: a) trans-1,4-cyclohexylene or cyclohexenylene, in which, in addition, one or more non-adjacent CH 2 groups may be replaced by -O- and/or -S- and in which H may be substituted by F, b) 1,4-phenylene, in which one or two CH groups may be replaced by N and in which, in addition, one or more H atoms may be replaced by Br, Cl, F, CN, methyl, methoxy or a mono- or polyfluorinated methyl or methoxy group, or c) a radical from the group 1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, cyclobutane-1,3-diyl, spiro[3.3]heptane-2,6-diyl, in which one or more hydrogen atoms may be replaced by F, CN, SCN, SF 5, CH 2 F, CHF 2, CF 3, OCH 2 F, OCHF 2 or OCF 3, one or more CH groups may be replaced by N, one or more double bonds may be replaced by single bonds, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, and Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, A 4 denotes V denotes H or F, Z 1 and Z 3 each, independently of one another, identically or differently, denote a single bond, -CH 2 O-, - O-, -CF 2 O-, -CH 2 CH 2 CF 2 O- -CF 2 CF 2 -, -CH 2 CF 2 -, -CH 2 CH 2 -, -(CH 2) 4 -, -CH=CH-, -CH=CF-, -CF=CF- or -C≡C-, where asymmetrical bridges may be oriented to both sides, a denotes 0, 1 or 2, b denotes 1, 2 or 3, and c denotes 0, 1 or 2, where a + b + c ≤ 4. R 1 denotes H, a halogenated or unsubstituted alkyl radical having 1 to 15 C atoms, where, in addition, one or more CH 2 groups in these radicals may each be replaced, independently of one another, by -C≡C-, -CH=CH-, - O-, -O -, - - or -O- in such a way that O atoms are not linked directly to one another, R 2 denotes F, Cl, OCF 3, OCHF 2, OCHFCF 3, OCF 2 CHFCF 3, CF 3, CN, SF 5, NCS, NCO, SCN or OCN, A 1, A 2 and A 3 each, independently of one another, identically or differently, denote: a) trans-1,4-cyclohexylene or cyclohexenylene, in which, in addition, one or more non-adjacent CH 2 groups may be replaced by -O- and/or -S- and in which H may be substituted by F, b) 1,4-phenylene, in which one or two CH groups may be replaced by N and in which, in addition, one or more H atoms may be replaced by Br, Cl, F, CN, methyl, methoxy or a mono- or polyfluorinated methyl or methoxy group, or c) a radical from the group 1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, cyclobutane-1,3-diyl, spiro[3.3]heptane-2,6-diyl, in which one or more hydrogen atoms may be replaced by F, CN, SCN, SF 5, CH 2 F, CHF 2, CF 3, OCH 2 F, OCHF 2 or OCF 3, one or more CH groups may be replaced by N, one or more double bonds may be replaced by single bonds, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, and Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, a) trans-1,4-cyclohexylene or cyclohexenylene, in which, in addition, one or more non-adjacent CH 2 groups may be replaced by -O- and/or -S- and in which H may be substituted by F, b) 1,4-phenylene, in which one or two CH groups may be replaced by N and in which, in addition, one or more H atoms may be replaced by Br, Cl, F, CN, methyl, methoxy or a mono- or polyfluorinated methyl or methoxy group, or c) a radical from the group 1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, cyclobutane-1,3-diyl, spiro[3.3]heptane-2,6-diyl, in which one or more hydrogen atoms may be replaced by F, CN, SCN, SF 5, CH 2 F, CHF 2, CF 3, OCH 2 F, OCHF 2 or OCF 3, one or more CH groups may be replaced by N, one or more double bonds may be replaced by single bonds, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, and Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, M denotes -O-, -S-, -CH 2 -, -CHY- or -CYY 1 -, and Y and Y 1 denote Cl, F, CN, OCF 3 or CF 3, A 4 denotes V denotes H or F, Z 1 and Z 3 each, independently of one another, identically or differently, denote a single bond, -CH 2 O-, - O-, -CF 2 O-, -CH 2 CH 2 CF 2 O- -CF 2 CF 2 -, -CH 2 CF 2 -, -CH 2 CH 2 -, -(CH 2) 4 -, -CH=CH-, -CH=CF-, -CF=CF- or -C≡C-, where asymmetrical bridges may be oriented to both sides, a denotes 0, 1 or 2, b denotes 1, 2 or 3, and c denotes 0, 1 or 2,