Eu(fod)3 binding on the 1H-NMR spectra of some benzo[3n]crown-n and dibenzo[3n+2]crown-n

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 1H-NMR spectra and the selective binding constants at 400 MHz and 305 K in CDCl3 were reported. The Eu(fod)3 interaction displayed the selective binding role of oxygen on macrocyclic, H2COCH2, backbones with o- or m-dioxyphenyl groups referring the 1H chemical shifts. The estimated equilibrium constants, Ka of 1:1 ratio of interactions were in accordance with the Eu3+ 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 Eu3+ complexes are more stable with larger ethyleneoxy groups.