Dipyrrinone chromophores, attached by their acid termini to give (1R, 2R)-cyclohexanediol dipropionate and diacetate esters (xanthobilirubinate and nor-xanthobilirubinate, respectively), interact through exciton coupling, as evidenced by intense bisignate circular dichroism Cotton effects for the pigment's long wavelength transition. The bis- xanthobilirubinate exhibits the expected negative exciton chirality (Δϵmax439-16, ...
