Structure characterization of strontium (II) bilirubinate complexes

Abstract

AbstractCalcium bilirubinate (CaBR) is the main component of pigment gallstones. At present no crystal structure of CaBR is available. Extended x‐ray absorption fine structure (EXAFS) is a powerful tool for local atomic structure determination, but it is difficult to measure the EXAFS spectra of calcium in compounds. Strontium bilirubinate (SrBR) was used instead of calcium, because of the similarity of IR spectra between CaBR and SrBR complexes. In this investigation a series of SrBR was synthesized. FTIR and EXAFS spectroscopic techniques were adapted to characterization. The results provide evidence of SrBR formation. It follows that the first shell about Sr (II) of the neutral BR compound consists of oxygen and nitrogen atoms with Sr‐O and Sr‐N distances of 2.61 Å and 2.69 Å, respectively. The coordination number of Sr is eight, consisting of four O atoms and four N atoms. It can lead to the unfolding of the coordination structure of CaBR. © 1995 John Wiley & Sons, Inc.