3H-​Indolium, 2-​[5-​[1-​[6-​[[2-​(2,​5-​dihydro-​2,​5-​dioxo-​1H-​pyrrol-​1-​yl)​ethyl]​amino]​-​6-​oxohexyl]​-​1,​3-​dihydro-​3,​3-​dimethyl-​2H-​indol-​2-​ylidene]​-​1,​3-​pentadien-​1-​yl]​-​1,​3,​3-​trimethyl-​, chloride (1:1)