SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS

Abstract

Complexation in M (II) – Rut systems (M(II) = Co, Cu) was studied by electron absorption spectroscopy and pH-metric titration in water-ethanol solutions depending on the metal: ligand ratio (1: 1; 2: 1) and the pH of the medium. It was shown that the structure and stoichiometric composition of the complexation reaction products are influenced by such basic parameters as L:M and the pH value of the medium. Depending on the pH value, chelation involves certain binding sites, which primarily is associated with the redistribution of the electron density in the flavonoid molecule. In a weakly acidic or neutral medium, regardless of the M(II): Rut ratio, the formation of monoligand complexes of rutin with 3-d metals occurs with the participation of 5-OH and 4-C=O fragments of the A and C rings, and in an alkaline medium, chelation proceeds on the catecholic fragment of ring B rutin. Biligand complexes are formed with the participation of the gydroxo groups of the catechol fragment of each rutin molecule, and the formation of compounds with a ratio of 2:1 occurs both due to 5-OH and 4C=O and due to 3 ', 4'-OH groups. The calculated values of the stability constants of the complexes showed that the stability of the Co (II) complexes is several orders of magnitude lower than the stability of the corresponding Cu (II) complexes.

Synthesis and Study of Spectral-luminescent and Biologically Active Properties of Mixed-ligand Complexes of Cobalt(II) and Copper(II) with Rutin and Glycine

“…The synthesis of mixed-ligand complexes was performed by the "block" method, taking into account the thermodynamic constants of stability of monolithic complexes. lgKst MRut and MGly complexes differ in several orders (lgKstCuGly2 = 15.66, lgKstCoGly2 = 9.16, [37] lgKstCuRut = 18.51), [34] therefore, MLCs are formed according to Scheme (Figure 2), when a complex with less stability acts as a "building block" for obtaining a multi-ligand compound by exocoordination of the second ligand.…”

“…We have previously studied rutin complexes with copper(II) and cobalt(II) in aqueous-ethanol solutions. [34] It is shown that in weakly acidic or neutral medium complexes Cu(II) and Co(II) with rutin are formed with the participation of 5-OH and 4-C=O fragments A and C of the ring, and in alkaline medium chelation occurs on the catechol fragment of ring B routine. In this case, the metal complexes have solvent molecules in the coordination environment, ie the coordination sphere of the metal is not completely saturated with the donor groups of the phenolate ligand.…”