Dialkyne compounds

A dialkyne compound of the formula I

• in which
• R1 and
• R2, independently of one another, are H, F, or an alkyl radical having 1-15 carbon atoms which is unsubstituted or monosubstituted to perhalo substituted by halogen or substituted by CN and in which, one or more CH2 groups are optionally, independently of one another, replaced by —O—, —S—, —CO—,
• in such a way that heteroatoms are not connected directly,
• X1, X2, X3
• and X4 are each, independently of one another, H or —C≡C—C≡C—R3, provided that at least one of the groups X1, X2, X3 and X4 is —C≡C—C≡C—R3,
• R3 is H, Cl, CN, SF5, CF3, or an alkyl radical having 1-15 carbon atoms which is unsubstituted or monosubstituted to perhalo substituted by halogen and in which, one or more CR2 groups are optionally replaced, in each case independently of one another, by —CH═CH— or —O— in such a way that —O— atoms are not connected directly,
• Q is —CH2— or —O—,
• Y1 and
• Y2, independently of one another, are C or Si,
• A1 and
• A2, independently of one another, are a trans-1,4-cyclohexylene radical which is unsubstituted or substituted by F or CN and in which, one or more non-adjacent CH2 groups are optionally replaced by —O— and/or —S—, or are
• Z1 and
• Z2 are each, independently of one another, —CO—O—, —O—CO—, 'CH2O—, —O—, —OCH2—, —CF2O—, —OCF2—, —CF2CF2—, —CF═CF—, —CH2CH2—, —CH═CH— or a single bond, and
• n and
• m, independently of one another, are 0, 1,2 or 3,
• where
• m+n is 1, 2 or 3,
• excluding compounds wherein X2 is —C≡C—C≡C—R3;
• R3 is H;
• X1, X3 and X4 are H;
• each Q is CH2;
• m is 0;
• Y1 and Y2 are each C;
• n is 1, Z1 is a single bond and A1 is unsubsrituted trans-1,4-cyclohexylene;
• and excluding compounds wherein X1 is —C≡C—C≡C—R3;
• R3 is H;
• X2, X3 and X4 are H;
• each O is CH2;
• n is 0;
• Y1 and Y2 are each C;
• m is 1, Z2 is a single bond and A2 is unsubstituted trans-1,4-cyclohexylene.