A Quantum-Chemical Investigation of the Geometry and NMR Chemical Shifts of Bilirubin

A computational investigation using density-functional-theory methods has been performed concerning the structure and nuclear magnetic resonance (NMR) chemical shifts of bilirubin with a special emphasis on the hydrogen bonds. Solid-state effects on the NMR spectra are investigated by considering a trimeric model derived from the available X-ray structure. Satisfactory agreement between theory and experiment is found with ring-current effects playing only a minor role for the interpretation of the solid-state NMR spectra. Authors' address: Jürgen Gauss, Institut für Physikalische Chemie, Universit?t Mainz, 55099 Mainz, Germany