| abstract |
A photochromic article comprising a host material and a photochromic amount of a photochromic compound or a structural isomer of the photochromic compound, the photochromic compound represented by the formula: <IMAGE> wherein R1, R2, R4, R5, R6, R8, A, B, C, and D are each selected from the group consisting essentially of hydrogen, a stable organic radical, a heterocyclic group, halogen, a nitrogen-substituted radical, and a nitrogen-substituted ring radical. |