Related Experiment Video
Updated: Jul 30, 2025
13:21
Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
15.0K
Electron Paramagnetic Resonance Spectra of Pentagonal Bipyramidal Gadolinium Complexes
Jonatan B Petersen1, You-Song Ding1,2, Sandeep Gupta3
1Department of Chemistry, School of Natural Science, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
Inorganic Chemistry
|May 12, 2023
Summary
This study investigates Gadolinium (Gd3+) complexes, revealing that zero-field splitting (ZFS) is primarily influenced by axial ligand strength. This finding offers insights into magnetic moment reversal barriers in related Dysprosium (Dy3+) complexes.
Area of Science:
- Coordination Chemistry
- Spectroscopy
- Magnetochemistry
Background:
- Gadolinium (Gd3+) exhibits near isotropic 4f7 configuration, making it unique for spectroscopic studies.
- Understanding ground state splitting in Gd3+ complexes is crucial for probing properties of other rare earth ions.
- Zero-field splitting (ZFS) in lanthanide complexes is key to their magnetic behavior and applications.
Purpose of the Study:
- To investigate the zero-field splitting (ZFS) in a series of Gd3+ pentagonal bipyramidal complexes.
- To determine the influence of axial and equatorial ligands on ZFS parameters.
- To correlate structural distortions with ZFS and magnetic properties.
Main Methods:
- Synthesis of Gd3+ pentagonal bipyramidal complexes with varying axial (X) and equatorial (Leq) ligands.
- Room-temperature continuous wave electron paramagnetic resonance (EPR) spectroscopy at X-, K-, and Q-bands.
- Fitting EPR spectra to a spin Hamiltonian using extended Stevens operators for C5 symmetry analysis.
Main Results:
- The zero-field splitting (ZFS) is dominated by the B20 term, strongly dependent on axial ligand donor strength.
- The magnitude of B20 is inversely proportional to the donor strength of axial ligands.
- Complex geometry and the X1-Gd-X2 angle correlate with the B65 parameter, indicating significant angular distortion effects.
Conclusions:
- Axial ligand donor strength is the primary determinant of ZFS in these Gd3+ complexes.
- Structural distortions, particularly the X1-Gd-X2 angle, significantly impact higher-order ZFS parameters.
- The ZFS parameter B20 is inversely proportional to the effective magnetic reversal barrier (Ueff) in isostructural Dy3+ complexes.
Related Concept Videos
03:02Colors and Magnetism
12.0K
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...
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...
12.0K
02:42Valence Bond Theory
8.9K
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...
8.9K
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
2.6K
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
2.6K
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
43.3K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
43.3K
02:58Crystal Field Theory - Octahedral Complexes
26.9K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
26.9K
01:22EDTA: Chemistry and Properties
2.0K
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...
2.0K