Electromerism
Encyclopedia
Electromerism is a type of isomerism between a pair of molecule
s (electromers, electro-isomers) differing in the way electron
s are distributed among the atoms and the connecting chemical bonds . In some literature electromerism is equated to valence tautomerism , a term usually reserved for tautomerism involving reconnecting chemical bonds .
One group of electromers are excited electronic states but isomerism is usually limited to ground state molecules. Another group of electromers are also called redox isomers: metal ions that can exchange their oxidation state
with their ligands (see non-innocent ligand
). One of the first instances was a cobalt bis(quinone) complex described by Buchanan and Pierpont in 1980 with a cobalt(II) complex in chemical equilibrium
with the cobalt(III) complex. Ligands commonly found are based on dioxolenes, phenoxyl radicals
and polychlorotriphenylmethyl radicals
. Metalloporphyrins have also been studied. A set of electromers not requiring redox-active ligands have been described as well as a set without a metal
Keywords:
Electromers, isomerism, non-innocent ligand
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s (electromers, electro-isomers) differing in the way electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s are distributed among the atoms and the connecting chemical bonds . In some literature electromerism is equated to valence tautomerism , a term usually reserved for tautomerism involving reconnecting chemical bonds .
One group of electromers are excited electronic states but isomerism is usually limited to ground state molecules. Another group of electromers are also called redox isomers: metal ions that can exchange their oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
with their ligands (see non-innocent ligand
Non-innocent ligand
In chemistry, a non-innocent ligand is a ligand in a metal complex where the oxidation state is unclear. Typically, complexes containing non-innocent ligands are redox active at mild potentials...
). One of the first instances was a cobalt bis(quinone) complex described by Buchanan and Pierpont in 1980 with a cobalt(II) complex in chemical equilibrium
Chemical equilibrium
In a chemical reaction, chemical equilibrium is the state in which the concentrations of the reactants and products have not yet changed with time. It occurs only in reversible reactions, and not in irreversible reactions. Usually, this state results when the forward reaction proceeds at the same...
with the cobalt(III) complex. Ligands commonly found are based on dioxolenes, phenoxyl radicals
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
and polychlorotriphenylmethyl radicals
Triphenylmethyl radical
The triphenylmethyl radical is a persistent radical and the first-ever radical described in organic chemistry. It can be prepared by homolysis of triphenylmethyl chloride 1 by a metal like silver or zinc in benzene or diethyl ether. The radical 2 forms a chemical equilibrium with the quinoid type...
. Metalloporphyrins have also been studied. A set of electromers not requiring redox-active ligands have been described as well as a set without a metal
Keywords:
Electromers, isomerism, non-innocent ligand
Non-innocent ligand
In chemistry, a non-innocent ligand is a ligand in a metal complex where the oxidation state is unclear. Typically, complexes containing non-innocent ligands are redox active at mild potentials...