Related Experiment Video
Updated: Jun 18, 2026
12:02
Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique
Published on: November 3, 2017
Direct evidence for a geometrically constrained "entatic state" effect on copper(II/I) electron-transfer kinetics as
1Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
Journal of the American Chemical Society
|June 14, 2001
Summary
The entatic state effect in copper complexes was quantitatively demonstrated for the first time. Electron transfer rates were measured for various copper complexes, revealing insights into constrained geometries and their impact on reactivity.
Area of Science:
- Inorganic Chemistry
- Bioinorganic Chemistry
- Physical Chemistry
Background:
- The "entatic" state, or constrained geometry, effect on electron transfer has lacked quantitative validation.
- Copper(II/I) complexes are crucial in biological systems and catalysis, making their electron transfer kinetics of significant interest.
Purpose of the Study:
- To quantitatively demonstrate the magnitude of the entatic state effect in copper(II/I) systems.
- To investigate the electron-transfer kinetics of closely related copper complexes with varying degrees of geometric constraint.
Main Methods:
- Synthesis and X-ray diffraction analysis of five Cu(II) and one Cu(I) complexes with diastereomers of [14]aneS(4) modified with cyclohexane.
- Determination of cross-reaction rate constants with six oxidants/reductants in aqueous solution.
- Calculation of electron self-exchange rate constants (k(11)) using Marcus cross relation.
- Evaluation of rate constants for metastable intermediates using stability constants from rapid-scan cyclic voltammetry.
Main Results:
- Evaluated 16 electron self-exchange rate constants for 8 related Cu(II/I) systems, spanning nearly 6 orders of magnitude.
- Identified a dual-pathway square scheme mechanism for the studied Cu(II/I) systems.
- Calculated specific self-exchange rate constants for strained intermediate species, with most falling within the 10(5)-10(6) M(-1) s(-1) range.
Conclusions:
- Provided the first unequivocal quantitative demonstration of the entatic state concept's efficacy in Cu(II/I) systems.
- The constrained geometries significantly influence electron transfer rates, comparable to those in blue copper proteins.
- This study offers a new framework for understanding electron transfer in metalloenzymes and synthetic catalysts.
More Related Videos
08:55Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
06:53Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Published on: June 9, 2023
Related Concept Videos
02:32Bonding in Metals
Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Drüde called the “Electron Sea Model”.
02:37Metallic Solids
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:17Theory of Metallic Conduction
The conduction of free electrons inside a conductor is best described by quantum mechanics. However, a classical model makes predictions close to the results of quantum mechanics. It is called the theory of metallic conduction.
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...