Abstract: Fourteen complexes of rare earth trichloride with L-cysteine were preparecd from aq. ethanol solution (Cc complex from aq. n-butanol) at pH3.5. The compounds have structu-ral formula RE(cys)₃Cl₃·3H₂O(RE=Cc-Lu and Y,except Pm). The main infrared absorption bands have been assigned. All the compounds may be classified into three groups: (1) complex of Ce which is a chain polynuclear complex with bridging bidentate ligand;(2)complexes of Pr-Ho and Y which are mononuclear complexes containing unidentate and che-lating bidentate ligands;(3) complexes of Er-Lu are the polymer containing unidentate,chelating bidentate and chelation-bridging tridentate ligands. Ln-O stretch vibration were observed at 412-428cm^-1 and 169-197cm^-1 The XPS study of Er-Lu complexes shows that the atoms of oxygen are coordinated to lanthanide ions. but chloride anions are not coordinated.

Key words: Rare carth complex, L-cysteine, FT-IR, XPS