摘要:
The photochromic compounds of the invention correspond to the formula: in which Th2 represents a bithienyl group in one of the positions 5 to 10 of the naphthenic ring system system, R1 denotes a bithienyl or trithienyl group and R2 denotes a bithienyl, trithienyl, aryl, naphthyl, thienyl, furyl, pyrrolyl or N-alkylpyrrolyl group.