Eufod
Encyclopedia
EuFOD is the chemical compound
with the formula Eu(OCC(CH3)3CHCOC3F7)3, also called Eu(fod)3. This coordination compound is used primarily as a shift reagent in NMR spectroscopy
. It is the premier member of the lanthanide
shift reagents and was popular in the 1970s and 1980s.
ligands bound to a Eu
(III) center. This metal atom has an electron configuration
of f6. The six electrons are unpaired—each in a different singly-occupied f-orbital—which makes the molecule highly paramagnetic. The complex is a Lewis acid
, being capable of expanding its coordination number of six to eight. The complex displays a particular affinity for "hard
" Lewis bases, such as the oxygen atom in ether
s and the nitrogen of amine
s. It is soluble in nonpolar solvents, even more so than related complexes of acetylacetone
and hexafluoroacetylacetone
. The fod ligand is a derivative of heptafluorobutyric acid
.
in the protons near any Lewis basic site to which it binds in a molecule. This change helps resolve closely spaced signals by separating the ones from these hydrogens away from others that are not near basic sites but whose normal chemical shift is similar. Only small amounts of shift reagents are used, because otherwise the paramagnetism of the reagent shortens the spin-lattice relaxation times of the nuclei
, which causes uncertainty broadening and loss of resolution. The availability of higher magnetic field spectrometers have lowered the demand for NMR shift reagents.
The original shift reagent was Eu(DPM)3, developed by Hinckley. Its structure is similar to EuFOD, but with tert-butyl groups in place of heptafluoropropyl substituents. That is, DPM- is the conjugate base derived from dipivaloylmethane, also known as 2,2,6,6-tetramethylheptane-3,5-dione. The ligand fod- is more lipophilic and by virtue of the perfluoralkyl substituent, its complexes are more Lewis acidic than those derived from DPM-.
in organic synthesis including stereoselective Diels-Alder and aldol addition reactions. For example, Eu(fod)3 catalyzes the cyclocondensations of substituted diene
s with aromatic and aliphatic aldehydes to yield dihydropyrans, with high selectivity for the endo
product.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula Eu(OCC(CH3)3CHCOC3F7)3, also called Eu(fod)3. This coordination compound is used primarily as a shift reagent in NMR spectroscopy
NMR spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained...
. It is the premier member of the lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
shift reagents and was popular in the 1970s and 1980s.
Structure and reactivity
Eu(fod)3 consists of three bidentate acetylacetonatoAcac
ACAC may refer to:* American Council for Accredited Certification, a private, non-profit certifying body* Atlanta Contemporary Art Center, a contemporary art museum in Atlanta* ACAC consortium, a subsidiary of China Aviation Industry Corporation...
ligands bound to a Eu
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
(III) center. This metal atom has an electron configuration
Electron configuration
In atomic physics and quantum chemistry, electron configuration is the arrangement of electrons of an atom, a molecule, or other physical structure...
of f6. The six electrons are unpaired—each in a different singly-occupied f-orbital—which makes the molecule highly paramagnetic. The complex is a Lewis acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
, being capable of expanding its coordination number of six to eight. The complex displays a particular affinity for "hard
HSAB theory
The HSAB concept is an acronym for 'hard and soft acids and bases. Also known as the Pearson acid base concept, HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways....
" Lewis bases, such as the oxygen atom in ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
s and the nitrogen of amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
s. It is soluble in nonpolar solvents, even more so than related complexes of acetylacetone
Acetylacetone
Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The less stable tautomer is a diketone formally named pentane-2,4-dione. The more common tautomer is the enol form. The pair of tautomers rapidly interconvert and are treated as a single...
and hexafluoroacetylacetone
Hexafluoroacetylacetone
Hexafluoroacetylacetone is the chemical compound with the formula CF3CCH2CCF3 . This colourless liquid is a ligand precursor and a reagent used in MOCVD...
. The fod ligand is a derivative of heptafluorobutyric acid
Heptafluorobutyric acid
Heptafluorobutyric acid is an organofluorine compound with the formula C3F7CO2H. As the fluorinated derivative of butyric acid, this colourless liquid is prepared by electrofluorination of the corresponding butyryl fluoride.-Applications:...
.
As an NMR shift reagent
The original application of Eu(fod)3 was for analyzing diastereomeric compounds in NMR spectroscopy. The paramagnetic compound induces additional chemical shiftChemical shift
In nuclear magnetic resonance spectroscopy, the chemical shift is the resonant frequency of a nucleus relative to a standard. Often the position and number of chemical shifts are diagnostic of the structure of a molecule...
in the protons near any Lewis basic site to which it binds in a molecule. This change helps resolve closely spaced signals by separating the ones from these hydrogens away from others that are not near basic sites but whose normal chemical shift is similar. Only small amounts of shift reagents are used, because otherwise the paramagnetism of the reagent shortens the spin-lattice relaxation times of the nuclei
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
, which causes uncertainty broadening and loss of resolution. The availability of higher magnetic field spectrometers have lowered the demand for NMR shift reagents.
The original shift reagent was Eu(DPM)3, developed by Hinckley. Its structure is similar to EuFOD, but with tert-butyl groups in place of heptafluoropropyl substituents. That is, DPM- is the conjugate base derived from dipivaloylmethane, also known as 2,2,6,6-tetramethylheptane-3,5-dione. The ligand fod- is more lipophilic and by virtue of the perfluoralkyl substituent, its complexes are more Lewis acidic than those derived from DPM-.
As a Lewis acid
Eu(fod)3 serves as a Lewis acid catalystCatalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
in organic synthesis including stereoselective Diels-Alder and aldol addition reactions. For example, Eu(fod)3 catalyzes the cyclocondensations of substituted diene
Diene
In organic chemistry a diene or diolefin is a hydrocarbon that contains two carbon double bonds.Conjugated dienes are functional groups, with a general formula of CnH2n-2. Dienes and alkynes are functional isomers...
s with aromatic and aliphatic aldehydes to yield dihydropyrans, with high selectivity for the endo
Endogenous
Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
product.