Synthesis and antioxidant activity of zinc(II) phthalocyanine tetranitroxide

Abstract

Zinc(II) phthalocyanine (np-TEMPO-ZnPc) bearing four TEMPO fragments at the non-peripheral positions of the macrocycle was prepared through the cyclotetramerization of phthalonitrile derivative 3-TEMPO-Pht. Characterization of tetraradical was performed by electron paramagnetic resonance (EPR) at room temperature. A characteristic triplet was observed (g = 2.00715, hyperfine coupling constant of 15.73 G) in the EPR spectrum of np-TEMPO-ZnPc measured in chloroform. The np-TEMPO-ZnPc was also investigated for in vitro antioxidant activities. Antioxidant properties were determined for its free radical scavenging effect, reducing power, beta-carotene bleaching and total antioxidant capacity assays. The results demonstrated that np-TEMPO-ZnPc has strong DPPH radical scavenging and beta-carotene bleaching activities even more than the standard antioxidant BHT. Especially, the compound exhibited similar radical scavenging effect at low concentrations when compared with BHT. (C) 2021 Elsevier Ltd. All rights reserved.