The complexing of Eu(fod)(3) with macrocyclic ethers, benzo[15]crown-5, benzo[12]crown-4, dibenzo[20]crown-6, dibenzo[23]crown-7 and dibenzo[26]crown-8 was observed on their (1)H-NMR spectra and the selective binding constants at 400 MHz and 305 K in CDCl(3) were reported. The Eu(fod)(3) interaction displayed the selective binding role of oxygen on macrocyclic, H(2)COCH(2), backbones with o- or m-dioxyphenyl groups referring the (1)H chemical shifts. The estimated equilibrium constants, K(a) of 1:1 ratio of interactions were in accordance with the Eu(3+) ionic radii to bind the oxygen sites depending on the macrocyclic size and conformation of the ethers. The minimum lanthanide-macrocyclic ether distance displayed the maximum stability so that benzo[3n]crown-n (n=4, 5) group was found to bind the Eu(fod)(3) moderately whilst dibenzo[3n+2]crown-n (n=6-8) oligomer chemical shifts were induced largely since the such Eu(3+) complexes are more stable with larger ethyleneoxy groups.