Synthesis and characterization for five 7,16-dibenzylated tetraaza[14]annulene nickel(II) complexes

Abstract

The substitution reaction of tetraaza[14]annulene nickel(II) ( 1) with five various para-substituted bezyl bromides led to the corresponding 7,16-dibenzylated complexes in 43–60% yields. The mass spectra indicate the existence of molecular ion peaks due to the 7,16-dibenzylated products. The macrocyclic skeleton of the five complexes and their electronic spectra are hardly changed by the benzylation. The five nickel(II) complexes are in almost square-planar coordination, judging from the ligand-field transition bands. The olefinic proton signals at the 7- and 16-positions disappear on benzylation in the 1H NMR spectra. The off-resonance decoupling peak at the 7- and 16-positions changes from a doublet to a singlet by the benzylation of 1 in 13C NMR spectra. The 13C NMR results are comparable with those of 1H NMR.