Abstract: Monolayer formation, LBfilm fabrication of bilirubin(1), its two kinds of amphiphilic derivatives, bilirubin dioctadecyl ester [B(COOC₁₈ H₃₇ )₂, 2] and dioctadecyl bilirubinamide [B(CONHC₁₈ H₃₇ )₂, 3] at an air water interface on subphases with different pHvalues and subphases containing different metal ions were investigated and compared with 1. Some information regarding the packing density in monolayers, molecular orientation and complexation by metal ions has been obtained by means of many physical measurements such as the π-Aisotherms, X-ray photoelectron spectroscopy, UV-visible spectroscopy and low angle X-ray diffraction. At the air water interface the amphiphilic ligands with their complexing head groups in contact with the aqueous phase can form metal complexes with many metal ions present in the aqueous phase. The formation of ligand-metal complexes leads to changes in the area per molecule and in the collapse pressure, as well as to changes in the XPS and UV-visible absorption spectra of the monolayer assemblies. Low-angle X-ray diffraction indicates that the LBfilms of 1, 2 and 3 were Y-type with bilayer spacing of ca. 2.50, 5.60 and 5.65 nm. The coordination in ordered molecular films are much different from that in bulk solution. It can help us to understand the formation and prevent and cure of gallstones.

Key words: Monolayer, Langmuir Blodgett films, Bilirubin derivatives, Acidity, Coordination