Jong-Wan Lim

Synthesis of 14-π nickel(II) complexes with disubstituted benzoN4 macrocycles and electrochemical studies of 14-π nickel(II) complexes with monosubstituted benzoN4 macrocycles

Abstract The template reaction of a 1:1 mixture of 4,5-disubstituted(2CH 3 or 2Cl)-1,2-phenylenediamine and alkylenediamine [NH 2 -(CH 2 ) n -NH 2 ; n =2 or 3] with 2,4-pentanedione in the presence of a nickel(II) salt gave a series of asymmetric 14-π nickel(II) complexes with disubstituted tetraazaannulene, [Ni(Me 4 -X 2 bzotetraaza[ Y ]ene)] (X=CH 3 and Cl, Y =14 and 15), which were characterized by mass, infrared, 1 H and 13 C NMR spectra. The electronic effects of the disubstituent groups on the phenyl ring significantly affected the spectral properties of the complexes. The electrochemical behaviors of the nickel(II) complexes with monosubstituted benzoN 4 macrocycles, [Ni(Me 4 -Xbzotetraaza[ Y ]ene)] (X=H, NO 3 , CH 3 and Cl, Y =14 and 15) exhibited cyclic voltammograms characterized by, two irreversible, one electron, waves due to oxidation of the macrocycle (Mc); Mc→Mc + in the ranges of +0.06–+0.28 V for 14-X and +0.01–+0.29 V for 15-X, and Mc + →Mc 2+ in the ranges of +0.58 to +0.81 V for 14-X and +0.36 to +0.79 V for 15-X versus Ag/Ag + (0.01 M AgNO 3 in 0.1 M tetraethylammonium perchlorate (TEAP) acetonitrile solution). In the reduction area only one reversible wave Ni 2+ /Ni + was detected at E 1/2 =−1.65 to −2.65 V in DMSO. The relationships between the oxidation potentials ( E ap ) and σ p were linear with a slopes of 0.23 V for 14-X and 0.18 or 0.23 V for 15-X (correlation coefficients of 0.99). The catalytic reduction of dioxygen by the electropolymerized glassy carbon electrodes (GCE) occurred at about 400 mV more positive than by the bared one. The catalytic reduction using 14-X occurred at potentials somewhat more positive than using 15-X.