Naphthaldehyde-derived ligands: synthesis and their Ni(II) ion complexation

Three novel diazacrown ether ligands, namely 17-, 18-, and 20-membered O2N2-donor macrocycles derived from 3,3 0 -(butane-1,4-diylbis(oxy))bis(2-naphtha- lenecarbaldehyde), were prepared and characterized by 1 H and 13 C NMR spectroscopy and mass spectra. Their host- guest interaction with Ni(II) was studied in DMSO-d6 using 1 H NMR spectroscopy. The stoichiometry of the complex in each case in the concentration range examined was determined to be 1:1 using the continuous variation method (Job's plot). The 17-membered O2N2-donor mac- rocycle in which the two nitrogen atoms are tethered by three methylene units binds Ni(II) more strongly than the other two macrocycles do.