Studies on Langmuir-Blodgett films of bilirubin and its amphiphilic derivatives

Monolayer formation, LB film fabrication of bilirubin(l), its two kinds of amphiphilic derivatives, bilirubin dioctadecyl ester [B(COOC18H37)(2), 2] a nd dioctadecyl bilirubinamide [B(CONHC18H37)(2), 3] at an air-water interfa ce on subphases with different pH values and subphases containing different metal ions were investigated and compared with 1. Some information regardi ng the packing density in monolayers, molecular orientation and complexatio n by metal ions has been obtained by means of many physical measurements su ch as the pi -A isotherms, X-ray photoelectron spectroscopy, UV-visible spe ctroscopy and low-angle X-ray diffraction. At the air-water interface the a mphiphilic ligands with their complexing head groups in contact with the aq ueous phase can form metal complexes with many metal ions present in the aq ueous phase. The formation of ligand-metal complexes leads to changes in th e 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 LB films of 1, 2 and 3 were Y-ty pe 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. I t can help us to understand the formation and prevent and cure of gallstone s.