Fluorine-containing liquid crystal compound, liquid crystal composition, and liquid crystal electro-optic element

A liquid crystal compound represented by formula (1)

• R1-(A1-Z1)a-(A2-Z2)b-(A3-Z3)c-A4-(CH2)n—CF═CF—R2 (1)
• wherein
• R1 is a hydrogen atom, or an alkyl group having 1 to 10 carbons,
• R2 is a halogen atom or an alkyl group having 1 to 10 carbons,
• at least one hydrogen atom in the alkyl group in R1 and R2 is optionally substituted with a halogen atom, and an ethereal oxygen atom or a thioethereal sulfur atom is optionally inserted between carbon-carbon atoms in the alkyl group or at a bond end of the alkyl group,
• A1, A2, A3 and A4 independently represent a phenylene group or a cyclohexylene group, wherein one or two —CH═ in the groups of A1, A2, A3 and A4 is optionally substituted with a nitrogen atom;
• and one or two —CH2— in these groups is optionally substituted with an ethereal oxygen atom or an thioethereal sulfur atom,
• Z1, Z2 and Z3 independently represent a single bond, —O—, —S—, or a divalent aliphatic hydrocarbon group having 1 to 4 carbons, wherein at least one hydrogen atom in the aliphatic hydrocarbon group is optionally substituted with a halogen atom, and an ethereal oxygen atom or a thioethereal sulfur atom is optionally inserted between carbon-carbon atoms in the aliphatic hydrocarbon group or at a bond end of the aliphatic hydrocarbon group,
• a, b, c independently represent 0 or 1, wherein a+b+c is 1 or greater,
• n is 0 or 2, wherein when A4 is a phenylene group, n is 2, and
• when A4 is a cyclohexylene group and n=0, R2 is an alkyl group having 1 to 10 carbons.