You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 5-[1,4-bis(7,7-dimethylindeno[2,1-b]carbazol-5-yl)phthalazin-6-yl]-7,7-dimethylindeno[2,1-b]carbazole .
user
C71H51N5
assistant