New heteroleptic Cu(II) complexes of chrysin with 2,2-bipyridine and substituted 1,10-phenanthrolines: synthesis, characterization, thermal stability and antioxidant activity

Abstract

In this study, the new heteroleptic Cu(II) complexes of chrysin were synthesized by using 2,2ꞌ–bipyridine and substituted 1,10–phenanthroline (1,10–phenanthroline, 4,7–dimethyl–1,10–phenanthroline or bathophenanthroline) co–ligands. The characterization of the obtained heteroleptic Cu(II) complexes were carried out by elemental analysis, ESI–MS, UV–visible and infrared spectral analyses, thermal analysis, magnetic susceptibility and molar conductivity measurements. In these complexes, chrysin, 2,2ꞌ–bipyridine, or substituted 1,10–phenanthrolines and Cu(II) ion were found in a ratio of 1: 1: 1. In addition, the resulting data supported square plane geometry for Cu(II) complexes. According to the results obtained, the proposed compositions are as follows: [Cu(chrH–1)(bpy)]ClO4·H2O (1, chrH = chrysin, bpy = 2,2′–bipyridine), [Cu(chrH–1)(phen)]ClO4.1.5H2O (2, phen = 1,10–phenanthroline), [Cu(chrH–1)(dmphen)]ClO4 (3, dmphen = 4,7–dimethyl–1,10–phenanthroline) and [Cu(chrH–1)(Bphen)]ClO4 (4, Bphen = Bathophenanthroline). Total phenolic contents and antioxidant capacities of Complexes 1–4 were measured by the Folin–Ciocalteu and ABTS (2,2′–azino–bis (3–ethylbenzothiazoline–6–sulfonic acid)) methods, respectively. According to the results, Complex 4 has the highest antioxidant capacity.