Related Experiment Video
Updated: Jan 11, 2026
09:45
Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
10.8K
Pentagonal Bipyramidal First-Row Transition Metal Complexes with Macrocyclic Ligand Containing Two Pyridine-N-Oxide
Bohuslav Drahoš1, Ivan Šalitroš2, Radovan Herchel1
1Department of Inorganic Chemistry, Faculty of Science, Palacký University Olomouc, 17. Listopadu 12, Olomouc CZ-77146, Czech Republic.
Inorganic Chemistry
|November 10, 2025
Summary
A novel pyridine-based macrocyclic ligand (L4) was synthesized and complexed with transition metals. The resulting complexes exhibit unique pentagonal bipyramidal structures and significant magnetic anisotropy, with one showing single-molecule magnet behavior.
Area of Science:
- Coordination Chemistry
- Materials Science
- Magnetochemistry
Background:
- Macrocyclic ligands are crucial in coordination chemistry for creating novel metal complexes.
- Pyridine-based ligands offer unique electronic and steric properties for metal binding.
- Understanding magnetic anisotropy in transition metal complexes is key for developing molecular magnetism.
Purpose of the Study:
- Synthesize a novel heptadentate pyridine-based macrocyclic ligand (L4) with pyridine-N-oxide pendant arms.
- Investigate the structural and magnetic properties of its first-row transition metal complexes.
- Explore the relationship between structure, magnetic anisotropy, and single-molecule magnet behavior.
Main Methods:
- Synthesis of the macrocyclic ligand L4 and its metal complexes [M(L4)](ClO4)2·DMF (M=Mn, Fe, Co, Ni).
- X-ray crystallography to determine the solid-state structures of the complexes.
- Magnetic susceptibility measurements and theoretical calculations to analyze magnetic anisotropy.
- Variable-temperature direct current and alternating current magnetic studies to investigate relaxation dynamics.
Main Results:
- The ligand L4 successfully formed complexes with Mn(II), Fe(II), Co(II), and Ni(II).
- X-ray structures revealed pentagonal bipyramidal geometries with significant Jahn-Teller distortion for the Ni(II) complex.
- Fe(II), Co(II), and Ni(II) complexes displayed pronounced magnetic anisotropy (D values provided).
- Complex 3 (Co(II)) exhibited field-induced single-molecule magnet behavior governed by direct and Raman relaxation processes.
Conclusions:
- The coordination ability of pendant arm functional groups significantly influences magnetic anisotropy.
- Pyridine-N-oxide pendant arms in L4 contribute to the observed magnetic properties.
- The study provides insights into the design of new molecular magnetic materials based on macrocyclic ligands.
Related Concept Videos
02:42Valence Bond Theory
11.1K
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...
11.1K
03:02Colors and Magnetism
13.9K
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...
13.9K
02:58Crystal Field Theory - Octahedral Complexes
30.5K
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...
30.5K
02:57Coordination Number and Geometry
18.8K
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.
18.8K
02:51Metal-Ligand Bonds
23.9K
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...
23.9K
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
48.0K
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,...
48.0K