Synthesis, characterization and structure of nickel(II) complexes of a 16-membered mixed-donor macrocyclic Schiff base ligand, potentially hexadentate, bearing two pendant alcohol functions

The reactions of NiX₂ · 6H₂O (X = Cl^-, ClO₄^-, NO₃^-) with a new macrocyclic Schiff base ligand (L = 8,9,18,19-tetrahydro-7H,17H-dibenzo[f,o][1,5,9,13]dioxadiaza cyclohexadecine-8,18-diol), potentially hexadentate containing two alcoholic pendant arms, have been investigated by template condensation of 2-[3-(2-formylphenoxy)-2-hydroxypropoxy]benzaldehyde and 1,3-diamino-2-propanol. The isolation of a selection of 1:1 (metal:ligand) complexes of nickel(II) has been carried out and IR and UV-Vis spectroscopy, conductance measurements and X-ray determination have been employed to probe the nature of the respective complexes in both solid and solution states. The UV-Vis spectra and X-ray determination indicate that the complexes are of the type [NiLX]X, with a distorted octahedral ligand field. However, the perchlorate complex of Ni(II) is of the [NiL(solv)]²⁺ form in solution. In all complexes, the potentially hexadentate ligand behaves as a pentadentate ligand.