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

Abstract Two new hexaazamacrocyclic nickel(II) complexes with the formula [NiL 1 (4-nba) 2 ] ( 1 ) and [NiL 2 (sal) 2 ] ( 2 ) (L 1  = 3,10-dioctyl-1,3,5,8,10,12-hexaazacyclotetradecane, L 2  = 3,10-diisobutyl-1,3,5,8,10,12-hexaazacyclotetradecane, 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 KPS 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.