Anion-pi interactions-interactions between benzo-crown ether metal cation complexes and counter ions
Rafał Frański1, Błazej Gierczyk, Grzegorz Schroeder
1Faculty of Chemistry, Adam Mickiewicz University, Poznań, Poland. franski@main.amu.edu.pl
Journal of the American Society for Mass Spectrometry
|November 8, 2008
Summary
Anion-pi interactions significantly influence copper and iron reduction in crown ether ions. Electron-deficient aromatic rings enhance anion interactions, hindering radical loss, while electron-rich rings promote it.
Area of Science:
- Mass Spectrometry
- Supramolecular Chemistry
- Physical Organic Chemistry
Background:
- Crown ethers are versatile macrocyclic compounds with applications in ion binding and sensing.
- In-source fragmentation in mass spectrometry provides insights into ion stability and reactivity.
- Anion-pi interactions, crucial in molecular recognition, influence the behavior of ions in the gas phase.
Purpose of the Study:
- To investigate the effect of aromatic ring electronics on the in-source fragmentation of metal-crown ether complexes.
- To elucidate the role of Anion-pi interactions in copper and iron reduction processes.
- To understand how substituent effects on the aromatic ring modulate ion stability and reactivity.
Main Methods:
- Electrospray ionization mass spectrometry (ESI-MS) was employed to generate and analyze metal-crown ether ions.
- In-source fragmentation at higher cone voltage was used to study radical loss pathways.
- Comparison of fragmentation patterns for crown ether ions with varying aromatic ring substituents (nitro, amino, unsubstituted).
Main Results:
- The loss of the counter ion radical (X(.)) during copper reduction was less efficient for electron-deficient nitro-substituted benzo-crown ethers due to enhanced Anion-pi interactions.
- Conversely, electron-rich amino-substituted benzo-crown ethers exhibited more facile loss of X(.) due to Anion-pi repulsion.
- Similar Anion-pi effects were observed in iron reduction, where the loss of a methoxy radical was influenced by the electronic nature of the aromatic ring.
Conclusions:
- Anion-pi interactions play a significant role in governing the fragmentation behavior of metal-crown ether ions.
- The electronic properties of the aromatic ring in crown ethers can be tuned to control Anion-pi interactions and subsequent ion stability.
- These findings have implications for designing selective ion sensors and understanding reaction mechanisms in supramolecular systems.
More Related Videos
06:561,3,5-Triphenylbenzene and Corannulene as Electron Receptors for Lithium Solvated Electron Solutions
Published on: October 10, 2016
10:52Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
Related Concept Videos
02:36Crown Ethers
Crown ethers are cyclic polyethers that contain multiple oxygen atoms, usually arranged in a regular pattern. The first crown ether was synthesized by Charles Pederson while working at DuPont in 1967. For this work, Pedersen was co-awarded the 1987 Nobel Prize in Chemistry. Crown ethers are named using the formula x-crown-y, where x is the total number of atoms in the ring and y is the number of ether oxygen atoms. The term 'crown' refers to the crown-like shape that these ether molecules take.
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...
01:19Complexation 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...
02:51Metal-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...
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...
02:48Ionic Bonding and Electron Transfer
Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence shell, and an anion (a negative ion) forms when a neutral atom gains one or more electrons in its valence shell. Compounds composed of ions are called ionic compounds (or salts), and their constituent ions are held together by ionic bonds: electrostatic forces of attraction between oppositely charged cations and anions.
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...