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Metal-Ligand Bonds

Metal-Ligand Bonds

The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...

Complexation Equilibria: The Chelate Effect

Complexation Equilibria: The Chelate Effect

In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...

Complexation Equilibria: Factors Influencing Stability of Complexes

Complexation 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...

Valence Bond Theory

Valence 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...

EDTA: Chemistry and Properties

EDTA: Chemistry and Properties

Polydentate ligands are most widely used in complexometric titrations because they form more stable complexes with the metal ions than mono- or bidentate ligands due to the chelate effect. Examples of polydentate ligands are ethylenediaminetetraacetic acid (EDTA), crown ethers, and cryptands. The most important feature of optimal polydentate ligands is the ability to form 1:1 complexes in a single-step process. Amino carboxylic acid derivatives are frequently used as complexing agents. EDTA is...

Coordination Number and Geometry

Coordination Number and Geometry

For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.

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Related Experiment Video

Updated: May 26, 2026

Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers

Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers

Published on: September 19, 2017

G-quadruplexes and metal ions.

Nancy H Campbell¹, Stephen Neidle

¹The School of Pharmacy, University of London, London, WC1N 1AX, UK.

Metal Ions in Life Sciences

|January 3, 2012

Summary

This summary is machine-generated.

Metal ions stabilize G-quadruplex structures, essential for DNA and RNA. This review surveys crystallographic data on these quadruplexes and their complexes, revealing structural insights into their stabilization mechanisms.

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In Vitro Chemical Mapping of G-Quadruplex DNA Structures by Bis-3-Chloropiperidines

In Vitro Chemical Mapping of G-Quadruplex DNA Structures by Bis-3-Chloropiperidines

Published on: May 12, 2023

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Last Updated: May 26, 2026

Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers

Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers

Published on: September 19, 2017

Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes

Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes

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In Vitro Chemical Mapping of G-Quadruplex DNA Structures by Bis-3-Chloropiperidines

In Vitro Chemical Mapping of G-Quadruplex DNA Structures by Bis-3-Chloropiperidines

Published on: May 12, 2023

Area of Science:

Biochemistry
Structural Biology
Biophysics

Background:

Quadruplex nucleic acids are stabilized by metal ions coordinating guanine O6 atoms.
G-quartets form the fundamental structural unit of quadruplexes.
Telomeric sequences from humans and ciliates are common sources for quadruplex formation.

Purpose of the Study:

To systematically survey crystallographic data on native quadruplexes.
To examine quadruplexes in complex with ligands and proteins.
To categorize quadruplex structures based on their molecularity.

Main Methods:

Systematic literature review of crystallographic data.
Analysis of structural data for native quadruplexes.
Categorization of quadruplexes into tetramolecular, bimolecular, and intramolecular types.

Main Results:

Detailed survey of crystallographic data on native quadruplexes and their complexes.
Identification and examination of three categories: tetramolecular, bimolecular, and intramolecular quadruplexes.
Focus on quadruplexes derived from human and ciliate telomeric sequences.

Conclusions:

Metal ion coordination is crucial for quadruplex stability.
Crystallographic data provides key insights into quadruplex structure and ligand interactions.
Understanding quadruplex structures is vital for potential therapeutic applications.