Synthesis and Characterizations of Asymmetrical Dibenzoylmonobenzotetraazacyclo[14]AnnuleneNickel(Ii) Complexes: X-Ray Structure of 3,10-DI(p-Chlorobenzoyl)-2,4,9,11-Tetramethyl-1,5,8,12-Monobenzotetraazacyclo[14]AnnuleneNickel(II)

Abstract

Asymmetric complexes, 3,10-di( p-Xbenzoyl)-2, 4,9,11-tetramethyl-1,5,8,12-monobenzotetraazacyclo[14]annulenenickel(II), with X¼CH 3 , H, Cl, NO 2 and OCH 3 , have been synthesized and characterized. IR spectra of benzoylated compounds show an intense band attributed to C¼O stretching in the region 1627-1655 cm À1 . Hammett plots of 1/ max of ! * and LMCT transitions have positive (þ 0.224) and negative slopes (À0.250), respectively. 1 H NMR spectra exhibit deshielding effects due to benzoyl groups, while methyl protons show shielding effects. Substituent effects in 1 H and 13 C NMR are similar. Voltammograms have two irreversible oxidation peaks due to the ligands in the ranges þ 290 to þ 350 mV and þ 540 to þ 600 mV, respectively. Reduction and oxidation peaks (metal-based) are found at þ 0.840 to þ 0.930 V and À2.580 to À2.840 V, respectively. Hammett plots of the first two oxidation potentials are linear with slopes of þ 0.028. Metal-based redox potentials (E op and E rp ) are dependent on substituents. The structure of the chloro-substituted complex 4 (orthorhombic, C222 1 , a ¼ 8.918(5), b ¼ 28.282(5), c ¼ 26.490(5) Å , Z ¼ 4, R1 ¼ 0.0392 and wR2 ¼ 0.0987) was solved using single-crystal X-ray diffraction methods.