US Patent 9034219 Photochromic compounds and compositions

Described herein are compounds generally comprising an indeno[2′,3′:3,4]naptho[1,2-b]pyran structure. Such compounds may be useful for their photochromic properties, and be used in certain photochromic compositions. Such compositions may further comprise other photochromic compositions and/or materials. Additionally, such compounds and/or compositions may be suitable for preparing certain photochromic articles. Also described herein are methods for preparing certain photochromic compounds, compositions, and articles.