| abstract |
Various photochromic materials are provided that are essentially free of polymerizable unsaturated groups, and comprise:n a) an indeno[2′,3′:3,4]naphtho[1,2-b]pyran; and b) an electron-withdrawing, non-conjugating group bonded at the 11-position of the indeno[2′,3′:3,4]naphtho[1,2-b]pyran. nn Alternative embodiments include various substituents at other positions of the indeno[2′,3′:3,4]naphtho[1,2-b]pyran. |