Patent ID: 8450503

Claim:
A compound reversibly convertible between a ring-open isomer (I)and a ring-closed isomer (II): wherein: each R 1 is independently H or a halogen; each R 2 is independently H or a halogen, or both R 2 when taken together form CH═CH; each R 3 is or a first R 3 is CO 2 Y (where Y is aryl or alkyl) and a second R 3 is aryl; each R 4 is aryl; and each R 5 is independently H, aryl or alkyl, and wherein the compound is convertible from said ring-open isomer (I) to said ring-closed isomer (II) under photochemical conditions and from said ring-closed isomer (II) to said ring-open isomer (I) under electrochemical conditions or photochemical conditions.