| http://www.w3.org/ns/prov#value | - [0038] The compound represented by the aforementioned general formula (3) forms an anhydrous ring containing 4 carbon atoms, and X represents oxygen atom or an NR group (wherein R is an alkyl group and/or hydroxyl alkyl group having from 2 to 16 carbon atoms). [0039] In addition, compounds represented by a general formula (4) can be cited as the basal nucleus of another diaryl ethene photochromic
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