Crown ether analogues and their complexes. Solid-state and solution stereochemistry of dibenzo-15-crown-4 ether and its 2:2 complex with sodium iodide as studied by X-ray crystallography and NMR spectroscopic methods
The structures of the title systems have been determined by X-ray crystallography. The sodium iodide complex has 2:2 stoichiometry and Ci symmetry. Each sodium cation coordinates to four oxygen atoms of one macrocyclic unit and one oxygen of the other 15-membered ring of the dimer. The 400 MHz 1H NMR spectra have been analysed and assignments made on the basis of NOESY and COSY experiments. Solution 13C NMR spectra have been assigned using HETCOR methods. Solid-phase 13C NMR spectra are included and the results of sodium complexation on the solid-phase 13C chemical shifts are discussed. [4-2H4] Dibenzo-15-crown-4 has been synthesized and employed as an aid in spectral assignments.