The present invention relates to alkyne compounds of the formula P1—Y1-A1-Y3-(T1-B1-)m-T3-C≡C-T4-(B2-T2-)n-Y4-A2-Y2—P2  (I) in which P1, P2 are each, independently of one another, hydrogen, C1-C12-alkyl, a polymerizable group or a group suitable for polymerization or a radical which carries a polymerizable group or a group suitable for polymerization, Y1, Y2, Y3, Y4 are each, independently of one another, a linking unit, B1, B2 are each, independently of one another, —C≡C— or a linking group as defined for Y1 to Y4, A1, A2 are each, independently of one another, a single chemical bond or a spacer having from one to 30 carbon atoms, T1, T2, T3, T4 are each, independently of one another, a divalent saturated or unsaturated carbocyclic or heterocyclic radical, and m, n are each, independently of one another, 0 or 1, with the proviso that at least one of the linking units Y3 or Y4 is a group —O—CO—O—, —O—CO—N(R)—, —(R)N—CO—O— or —(R)N—CO—N(R)—. The invention further relates to nonpolymerizable and polymerizable liquid-crystalline compositions comprising at least one alkyne compound of the formula I according to the invention, the use of these nonpolymerizable and polymerizable liquid-crystalline compositions for producing optical components, the use of the polymerizable liquid-crystalline compositions for printing or coating substrates, for preparing dispersions and emulsions, for producing films and pigments and optical components, printed or coated substrates, dispersions and emulsions, films and pigments of this type.