The luminescent Er(III)-chelated complexes based on coumarin derivatives such, as acid, and coumarin 343 were prepared,4 by ligand-exchange reaction. in. the presence of ErCl3 and potassium coumarin derivative salts. The chemical structures of Me present complexes were confirmed by elementary analysis, thermal gravimetric analysis FT-IR, absorption and emission. spectroscopies. The coumarin-based, Er(III) complexes exhibited the near IR emission, corresponding to Me characteristic I-3(13/2)-->I-3(15/2) transitiom of trivalent erbium ions, taking place in the region of 1512 or 1530nm. Their PL intensity also depends on. the degree of the spectral overlap between. the emission band of coumarin derivative and the absorption band Er ion.