Comparative study of donor atom effects on the thermodynamic and electron-transfer kinetic properties of copper(ii/i) complexes with sexadentate macrocyclic ligands. [Cu^II/I([18]aneS₄N₂)] and [Cu^II/I([18]aneS₄O₂)]

Abstract

Studies have been conducted on the copper complexes formed with two sexadentate macrocyclic ligands containing four thioether sulfur donor atoms plus either two nitrogen or two oxygen donor atoms on opposing sides of the ring. The resulting two ligands, L, designated as [18]aneS(4)N(2) and [18]aneS(4)O(2), respectively, represent homologues of the previously studied Cu(ii/i) system with a macrocycle having six sulfur donor atoms, [18]aneS(6). Crystal structures of [Cu(II)([18]aneS(4)O(2))](ClO(4))(2) and [Cu(I)([18]aneS(4)O(2))]ClO(4) have been determined in this work. Comparison of the structures of all three systems reveals that the oxidized complexes are six coordinate with two coordinate bonds undergoing rupture upon reduction. However, the geometric changes accompanying electron transfer appear to differ for the three systems. The stability constants and electrochemical properties of both of the heteromacrocyclic complexes have been determined in acetonitrile and the Cu(II/I)L electron-transfer kinetics have been studied in the same solvent using six different counter reagents for each system. The electron self-exchange rate constants have then been calculated using the Marcus cross relationship. The results are compared to other Cu(II/I)L systems in terms of the effect of ligand geometric changes upon the overall kinetic behavior.

Kinetics of Regeneration and Recombination Reactions in Dye-Sensitized Solar Cells Employing Cobalt Redox Shuttles

“…The self-exchange rate constant, k 11 , for [Fe­(C 5 H 4 CH 3 ) 2 ] +/0 has been reported previously, using NMR analysis, to be (8.3 ± 0.8) × 10 6 M –1 s –1 . Using this value for k 11 , the self-exchange rate constant for [Co­(bpy) 3 ] 3+/2+ , k 22 , was calculated to be 0.27 ± 0.06 M –1 s –1 , which is in reasonable agreement with a literature value of 0.645 M –1 s –1 , especially considering that it was measured under similar, but different, conditions and crossed with a different redox couple. , The determined self-exchange rate constant for [Co­(bpy) 3 ] 3+/2+ was then used to determine a value of (9.1 ± 0.7) × 10 3 M –1 s –1 , k 33 , for the [Co­(ttcn) 2 ] 3+/2+ self-exchange reaction. A summary of the self-exchange rate constants can be found in Table .…”

CuI Complexes with N,N′,S,S′ Scorpionate Ligands: Evidence for Dimer−Monomer Equilibria

“…The underlying idea is to design geometrically preorganized ligands with a suitable donor set that satisfies the electronic and steric requirements of Cu I , to yield mononuclear complexes exhibiting a tetrahedral geometry of the metal center. The reason for this resides in the possible exploitation of low-molecular-weight complexes as functional models of type-1 cupredoxins (electron-transfer copper proteins). – Some of these models have recently been studied as electron-transfer mediators in dye-sensitized solar cells …”

A convenient approach to amphiphilic hyperbranched polymers with thioether shell for the preparation and stabilization of coinage metal (Cu, Ag, Au) nanoparticles

“…However, in the presence of thiolated hyperbranched polyglycerols it becomes soluble, as confirmed by the direct visual observation of the resulting green solution and by the UV–vis spectrum shown in Figure . Several polythioether ligands that complex copper(II) have been reported to date, and a high complexation constant K Cu(II)‐thioether = 10 8 was found . In the absence of polymer, the UV–vis spectrum of the copper(II) precursor in methanol is characterized by a weak absorption band centered at 800 nm assigned to the well‐known d–d transition for Cu 2+ ions .…”