Spirooxazine radical derivatives and reversible isomerization reaction

Spirooxazine radical compounds of the following formula (1):

• wherein,
• X1 is a chalcogen element, alkylidene or cycloalkylidene group;
• X2 is an oxygen atom;
• R1 to R11 are, independently each other, hydrogen atom, alkyl with 1˜4 carbons, alkoxy, aryl, halogenated alkyl, cyano, amino, or nitro group, or halogen atom, or, any of R1 to R11 bonded to carbon atoms adjacent to each other may form in combination an aromatic or heterocyclic ring, wherein optionally the aromatic or heterocyclic ring is substituted with an electron donor such as alkyl, alkoxy, or amino group or an electron acceptor such as nitro, cyano, halogenated alkyl, alkyl-carbonyl, alkyl-ester, or halogen group;
• and
• n is 0 or 1.