3H-​Indolium, 2-​[2-​[2-​chloro-​3-​[2-​[1-​[6-​[(2,​5-​dioxo-​1-​pyrrolidinyl)​oxy]​-​6-​oxohexyl]​-​1,​3-​dihydro-​3,​3-​dimethyl-​2H-​indol-​2-​ylidene]​ethylidene]​-​1-​cyclohexen-​1-​yl]​ethenyl]​-​1-​[6-​[(2,​5-​dioxo-​1-​pyrrolidinyl)​oxy]​-​6-​oxo