Tetracyclic liquid crystal compound having diatomic bonding group and 2,3-difluorophenylene, liquid crystal composition and liquid crystal display device

A compound, represented by formula (1):

• wherein, in formula (1),
• R1 is alkyl having 1 to 15 carbons, and in the alkyl, at least one piece of —CH2— may be replaced by —O—, and at least one piece of —CH2CH2— may be replaced by —CH═CH—, and R2 is alkyl having 1 to 15 carbons, alkoxy having 1 to 15 carbons or alkenyl having 2 to 15 carbons;
• ring A1 and ring A2 are independently 1,4-cyclohexylene, 1,4-phenylene, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, pyridine-2,5-diyl or pyrimidine-2,5-diyl, and ring A3 is 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, pyridine-2,5-diyl or pyrimidine-2,5-diyl;
• and
• Z1, Z2 and Z3 are independently a single bond, —CH2CH2— or —CH═CH—, and at least one of Z1, Z2 and Z3 is —OCO—, —CH2CH2— or —CH═CH—,
• in which, when ring A3 is 2-fluoro-1,4-phenylene, at least one of ring A1 and ring A2 is 1,4-phenylene, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, pyridine-2,5-diyl or pyrimidine-2,5-diyl, and Z3 is a single bond,
• in which, when R1 is CH2═CH— or alkenyloxy, Z1 and Z3 each are a single bond and Z2 is —CH═CH—, at least one of ring A1, ring A2 and ring A3 is 1,4-phenylene, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, pyridine-2,5-diyl or pyrimidine-2,5-diyl.