Liquid crystal compound, liquid crystal composition and liquid crystal display device

A compound represented by formula (I):

• wherein, in formula (I), R1 is fluorine, chlorine, or alkyl having 1 to 10 carbons, and in the alkyl, at least one of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, and at least one of —(CH2)2— may be replaced by —CH═CH— or —C≡C—;
• α and β are independently cyclohexane-1,3,5-triyl or benzene-1,3,5-triyl, and in the rings, —CH2— may be replaced by —O—, —CH— may be replaced by —N—, and —(CH2)2— may be replaced by —CH═CH—, and in the rings, at least one of hydrogen may be replaced by fluorine, chlorine, —CF3, —CHF2, —CH2F, —OCF3, —OCHF2 or —OCH2F;
• Z is a single bond or unbranched alkylene having 1 to 4 carbons, and in the alkylene, at least one of —CH2— may be replaced by —O—, —CO—, —S— or —SiH2—, at least one of —(CH2)2— may replaced by —CH═CH— or —C≡C—, and at least one of hydrogen may be replaced by fluorine;
• and
• MG is represented by formula (II):
• wherein, in formula (II), Sp is a single bond or unbranched alkylene having 1 to 10 carbons, and in the alkylene, at least one of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, and at least one of —(CH2)2— may replaced by —CH═CH— or —C≡C—;
• Ra is independently fluorine, chlorine, or unbranched alkyl having 1 to 10 carbons, and in the alkyl, at least one of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, and at least one of —(CH2)2— may be replaced by —CH═CH— or —C≡C—;
• A1, A2, A3 and A4 are independently 1,4-cyclohexylene, 1,4-phenylene, cyclohexene-1,4-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl or naphthalene-2,6-diyl, and in the rings, one of —CH2— may be replaced by —O—,—S—, —CO— or —SiH2—, and at least one of —(CH2)2— may be replaced by —CH═CH—, and in the rings, at least one of hydrogen may be replaced by fluorine, chlorine, —CF3, —CHF2, —CH2F, —OCF3, —OCHF2 or —OCH2F;
• Z1, Z2, Z3 and Z4 are independently a single bond or alkylene having 1 to 4 carbons, and in the alkylene, at least one of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, at least one of —(CH2)2— may be replaced by —CH═CH— or —C≡C—, and at least one of hydrogen may be replaced by fluorine;
• and m, n, q and r are independently 0, 1 or 2, and a sum of m, n, q and r is 2, 3, 4 or 5.