Wavelength Dependence of Quantum Yields and Product Distribution in the Anaerobic Photochemistry of Bilirubin Dimethyl Ester

Abstract— ( Z,Z )‐Bilirubin dimethyl ester exists in two or more forms in solution, and photorearranges to the ( E,Z )‐ and ( Z,E )‐isomers. Deaerated solutions of bilirubin dimethyl ester in 2‐methyltetrahydrofuran and chloroform/ethanol were irradiated with light of 10nm bandwidth in the range 380–470 nm at room temperature. Absorption difference spectroscopy showed that the solution forms of bilirubin dimethyl ester differ in their photoreactivity, and that the quantum yields of their disappearance and the distribution of the photorearrangement isomers are wavelength dependent.