Syntheses, crystal structures, spectroscopy, and catalytic properties of two nickel-based hexaazamacrocyclic complexes with carboxylate ligands

Two new hexaazamacrocyclic nickel(II) complexes with the formula [NiL1 (4-nba)(2)] (1) and [NiL2(sal)(2)] (2) (L-1 = 3,10-diocty1-1,3,5,8,10,12-hexaazacyclotetradecane, L-2 = 3,10-diisobuty1-1,3,5,8,10,12-hexaazacydotetradecane, 4-nba = p-nitrobenzoate, and sal = salicylate) were synthesized at room temperature. These complexes were characterized by physico-chemical and spectroscopic methods as well as single-crystal X-ray diffraction analysis. The coordination geometry in complexes 1 and 2 exhibit a distorted octahedron around the nickel(II) ion with hexaazamacrocyclic unit in the equatorial positions and two p-nitrobenzoate (or salicylate) anions in the axial positions. The degradation of methyl orange by potassium persulfate (KPS) in the presence of complex 1 (or 2) oxidation system occurred to near completion in 60 min compared to only 55% with KIDS alone under UV light irradiation. Thus, both complexes in cooperation with KPS could be an attractive choice for degradation of organic pollutants for environmental remediation. (C) 2017 Elsevier B.V. All rights reserved.