Abstract: A liquid crystalline compound has excellent liquid crystal properties, particularly high phase transition temperature. Diamantane compounds are represented by the general formula (I): (I) wherein A and B are each a six-membered, saturated or unsaturated, carbo- or hetero-cycle, and these cycles may have substituents, which substituents may be united to form a ring; and R1 and R2 are each a hydrocarbon group having 1 to 18 carbon atoms, and part of the carbon atoms of the hydrocarbon group may be replaced by heteroatoms or heteroatom-containing groups, while part of the hydrogen atoms thereof may be replaced by halogen atoms or heteroatom-containing groups.

Abstract: A liquid crystalline compound has excellent liquid crystal properties, particularly high phase transition temperature. Diamantane compounds are represented by the general formula (I): (I) wherein A and B are each a six-membered, saturated or unsaturated, carbo- or hetero-cycle, and these cycles may have substituents, which substituents may be united to form a ring; and R1 and R2 are each a hydrocarbon group having 1 to 18 carbon atoms, and part of the carbon atoms of the hydrocarbon group may be replaced by heteroatoms or heteroatom-containing groups, while part of the hydrogen atoms thereof may be replaced by halogen atoms or heteroatom-containing groups.

Abstract: [Problem] To provide a photochromic compound that is rapidly colored upon irradiation with ultraviolet light, and is rapidly decolored rapidly upon heat application after termination of irradiation with ultraviolet light, and to provide a process for producing the same. [Means for Solving Problems] A photochromic compound represented by general formula (I). R1, R2 and R3 are each a hydrogen atom; a functional group containing an atom in groups 15-16 of the periodic table; a halogen atom; a hydrocarbon group optionally substituted with said functional group or a halogen atom; or an optionally substituted heterocyclic group. R1 and R2 as well as R2 and R3 may be bonded to each other to form an optionally substituted carbon or heterocyclic ring. Z is a polymantylidene group. W is a divalent organic group that forms an optionally substituted carbon aromatic or heterocyclic aromatic ring together with the carbon-carbon double bond to which it is bonded.