Eu(fod)3 binding on the 1H‐NMR spectra of bis(2′‐ethylbenzoate)ethylene glycol podands

Abstract

The complexing and selective binding constants of Eu(fod)(3) with bis(2'-ethylbenzoate)ethylene glycol podands having one to four oxyethylene groups was observed on their (1)H-NMR spectra at 250 MHz and 295 K in CDCl(3). The Eu(fod)(3) interaction displayed the selective binding role of oxygen on H(2)C-O-CH(2) backbones with referring the (1)H chemical shifts. The estimated equilibrium constants, K(a), of 1:1 ratio of interactions were in accordance with the Eu(fod)(3) ionic radii to bind the oxygen sites depending on the size and conformation of the esters. Esters having one or two ethyleneoxy groups gave mainly 2:2 complexes using ester sites. The minimum lanthanide-podand ester distance displayed the maximum stability so that ester with four oxyethylene groups was found to bind the Eu(fod)(3) moderately, whereas ester with three oxyethylene groups showed a large induced chemical shift due to the stability of Eu(3+) complexes with larger ethyleneoxy groups.