Compound, liquid-crystal composition and optical material

A compound represented by the following formula (1) and exhibiting a smectic liquid-crystal phase:

• R1—(Ar1)p—C≡C—(Ar2)m—C≡C—(Ar3)n—R2 (1)
• wherein R1 and R2 each represent an alkyl group having at least 10 carbon atoms, wherein at least one —CH2— in the alkyl group may be substituted with any of —C≡C—, —C(R3)═C(R4)—, —CO—, —O—, —S—, —CO2—, —OCO—, —CON(R5)—, —N(R6)CO— and —C(R3)(—O—)C(R4)—;
• R3, R4, R5 and R6 each represent a hydrogen atom or an alkyl group;
• Ar1 and Ar3 each represent a halogen-substituted divalent aromatic hydrocarbon group;
• Ar2 represents a nitrogen-containing 6-membered heterocyclic group;
• and p, m and n each indicate 1 or 2.