A coordination polymer [Er(CCA)₃(H₂O)₂]_n•2nH₂O (HCCA＝coumarin-3-carboxylic acid) has been prepared by solvent-thermal method and characterized by elemental analysis and IR spectra and single crystal X-ray diffraction. The crystal of erbium(III) complex belongs to monoclinic system with space group, P2₁/c, a＝0.6310(1) nm, b＝1.4165(2) nm, c＝3.1731(3) nm|β＝91.861(2)°, V＝2.8346(7) nm³, D_c＝1.890 g•cm^－3, Z＝4, F(000)＝1596, residual factors R₁＝0.0525, wR₂＝0.0930 [I＞2σ(I)], S＝1.290. The Er(III) atom is eight-coordinated by eight O atoms from three ligands (CCA) and two coordinated water molecules, and the coordination polyhedron around the Er(III) atom can be best described as a distorted dodecahedron geometry. Two adjacent Er(III) atoms were bridged into a one-dimensional polymeric chain by the carboxylic group in a ligand (CCA). The interaction between complex and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy at different temperature. The results indicated that the complex quenches the fluorescence of BSA through a static quenching procedure. The binding constants (K_a) and the number of binding sites (n) between the complex and BSA were calculated at different temperature. The corresponding thermodynamic parameters enthalpy changes (ΔH＞0) and entropy changes (ΔS＞0) were also obtained according to the vant Hoff equation. The primary binding pattern between complex and BSA was interpreted as hydrophobic interaction. The binding average distance r between the donor (BSA) and acceptor (complex) was obtained to be 2.85 nm based on the F?sters theory, which indicates the non-radiation energy transfer can occur from BSA to complex with high probability.

Key words: erbium(III) coordination polymer, coumarin-3-carboxylic acid, crystal structure, bovine serum albumin (BSA), fluorescence spectra, solvent-thermal method