3H-​Indolium, 1-​(5-​carboxypentyl)​-​2-​[2-​[3-​[2-​[1-​(5-​carboxypentyl)​-​1,​3-​dihydro-​3,​3-​dimethyl-​2H-​indol-​2-​ylidene]​ethylidene]​-​2-​chloro-​1-​cyclohexen-​1-​yl]​ethenyl]​-​3,​3-​dimethyl-​, bromide (1:1)