LIQUID CRYSTAL COMPOUND HAVING XANTHENE SKELETON AND EXHIBITING NEGATIVE DIELECTRIC ANISOTROPY, LIQUID CRYSTAL COMPOSITION AND LIQUID CRYSTAL DISPLAY DEVICE

A liquid crystal compound satisfies at least one of physical properties such as a high stability to heat, light and so forth, a high clearing point, a low minimum temperature of a liquid crystal phase, a small viscosity, a suitable optical anisotropy, a large negative dielectric anisotropy, a suitable elastic constant and an excellent compatibility with other liquid crystal compounds. The compound is represented by formula (1). In the formula, for example, R1 and R2 are alkyl having 1 to 15 carbons; ring A1 and ring A2 are 1,4-cyclohexylene or 1,4-phenylene, Z1 and Z2 are a single bond, -(CH2)2-, -CH CH-, -C≡C-, -COO-, -OCO-, -CH2O-, -OCH2-, -CF2O-, -OCF2- or -CF CF-, a and b are 0, 1 or 2, and a sum of a and b is 1 or 2.