Chalcone and Flavonol Copper(II) Complexes Containing Schiff Base Co-Ligand: Synthesis, Crystal Structures and Catecholase-like Activity

Abstract

Four new heteroleptic copper(II) complexes having chalcone or flavonol ligands and Schiff base (N-phenyl-5-chlorosalicylideneimine) as co-ligand were prepared, chemically and structurally characterized and investigated as functional biomimetic catecholase models. The complexes were prepared by the solution synthesis and crystal and molecular structures were determined by X-ray diffraction. Complexes were chemically characterized by elemental analysis, infrared and electronic absorption spectroscopy as well as by electrochemical measurements. Copper(II) chalcone complexes, with square-pyramidal CuO4N core, are binuclear, featuring phenolate oxygen from the Schiff base as a bridging atom, while copper(II) flavonol complexes are mononuclear, and reveal a square planar CuO3N coordination core. Catalytic activity of the complexes in 3,5-di-tert-butylcatechol oxidation was confirmed by spectrophotometric and electrochemical measurements. Kinetic measurements revealed that the binuclear (chalcone-containing) complexes have enhanced catalytic activity as compared to the mononuclear Cu(II) flavonol complexes. Relatively high kcat values (300-750 h-1) confirmed their respectable biomimetic catecholase-like activity.

Overview of the Antioxidant and Anti-Inflammatory Activities of Selected Plant Compounds and Their Metal Ions Complexes

“…The crystal structure of four Cu-flavonoid complexes: [Cu(Flav- O , O )(oxphen- N , O )] [ 274 ], [Cu(Flav- O , O )(oxphen- N , O )] [ 274 ] and [Cu(Flav- O , O )(bipy- N , N )] [ 275 ] and [Cu(Flav- O , O ) 2 ] [ 276 ] are coordinated in the bidentate chelating mode by O , O atoms from the flavonoid part and N , N / O from the co-ligands. Four of the Cu(II) complexes are four-coordinated, with a slightly distorted square planar geometry, while the complex [Cu(Flav- O , O )(PPh 3 ) 2 ] [ 276 ] has tetrahedral geometry with (Flav- O , O ) ligand coordinated in bidentate mode and two monodentate PPh 3 .…”

Synthesis, Crystal Structure, and Optical Properties of Mononuclear Eu(III) and Tb(III) Complexes Containing a Chalcone Ligand

“…In this complex, the chalcone coordinates as chelating bidentate ligand, and the emissive properties are influenced by the aggregation modes of the mononuclear complexes. Other chalcones derived from 2 -hydroxyacetophenone were employed for synthesis of heteroleptic Cu(II) [10][11][12][13], Zn(II) [13], Ni(II) [14], or Ru(II) complexes [15][16][17][18]. These chalcones also act as chelating bidentate monoanionic ligands (by deprotonation of the phenol group).…”

Catecholase Activity and Substituent Effect of New Homoleptic Copper(ii) Chalcone Complexes

“…Recent studies present that copper(II) chalcone complexes show evidence of catalysis in the oxidation reaction of catechol to o-quinone under atmospheric dioxygen [2,14,15]. The catalyzing potential of two novel copper complexes of chalcone derivatives in the oxidation reaction of catechol to o-quinone was investigated by Kahrović et al [16]. We report the synthesis of three novel neutral copper(II) complexes (1-3) containing chalcone ligands including the study of their catalytic activity towards the 3,5-di-tert-butylcatechol oxidation.…”