Patent ID: 7556751

Claim:
A photochromic material representable by the following structure III: wherein R 16 is a first electron withdrawing group having a Hammett σ p value of from 0.05 to 0.75; R 17 is: hydrogen, or a second electron withdrawing group having a Hammett σ p value of from 0.05 to 0.75; q is the integer 0, and s is the integer 0; R 19 and R 20 are each independently: hydrogen; C 1 -C 6 alkyl; C 3 -C 7 cycloalkyl; allyl; substituted or unsubstituted phenyl; substituted or unsubstituted benzyl; chloro; fluoro; the group —C(═O)W, wherein W is hydrogen, hydroxy, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, the unsubstituted, mono- or disubstituted aryl groups phenyl or naphthyl, phenoxy, mono- or di-(C 1 -C 6 )alkoxy substituted phenoxy, mono- or di-(C 1 -C 6 )alkoxy substituted phenoxy, amino, mono(C 1 -C 6 )alkylamino, di(C 1 -C 6 )alkylamino, phenylamino, mono- or di-(C 1 -C 6 )alkyl substituted phenylamino, or mono- or di-(C 1 -C 6 )alkoxy substituted phenylamino; or R 19 and R 20 together form a spiro-carbocyclic group containing 3 to 6 carbon atoms, or a spiro-heterocyclic group containing 1 to 2 oxygen atoms and 3 to 6 carbon atoms including the spirocarbon atom, said spiro-carbocyclic and spiro-heterocyclic groups being annellated with 0, 1 or 2 benzene rings, provided that substitution at the carbon to which R 19 and R 20 are attached does not comprise hydroxyl; and B and B′ are each independently an unsubstituted, or substituted aryl group that has at least one pi-bond capable of being in conjugation with the pi-system of the open form of the core indeno-fused naphthopyran structure, provided that substitution at the 13-position of the indeno-fused naphthopyran does not comprise hydroxyl.