Related Experiment Video
Updated: Sep 25, 2025
06:53
Author Spotlight: Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Published on: June 9, 2023
2.1K
Two-dimensional square-grid iron(ii) coordination polymers showing anion-dependent spin crossover behavior
Jong Won Shin1, Ah Rim Jeong1, Jong Hwa Jeong1
1Department of Chemistry, Kyungpook National University Daegu 41566 Republic of Korea jeongjh@knu.ac.kr.
RSC Advances
|May 2, 2022
Summary
This study presents two new iron(ii) coordination polymers with square-grid frameworks. Compound 2 exhibits unique two-step spin crossover behavior due to selenocyanate ligands, transitioning between high-spin and low-spin states.
Area of Science:
- Materials Chemistry
- Coordination Chemistry
- Solid-State Chemistry
Background:
- Coordination polymers offer tunable properties based on metal ions and organic linkers.
- Spin crossover (SCO) materials based on iron(ii) are of interest for molecular switches and sensors.
- Square-grid coordination polymers provide unique structural motifs for exploring magnetic phenomena.
Purpose of the Study:
- To synthesize and characterize novel Fe(ii)-based coordination polymers.
- To investigate the magnetic properties, specifically spin crossover behavior, of the synthesized compounds.
- To elucidate the structural basis for the observed magnetic transitions.
Main Methods:
- Solvothermal synthesis of coordination polymers using FeSO4·7H2O, N,N,N',N'-tetrakis(pyridin-4-yl)methanediamine (tpmd), and KNCS/KNCSe.
- Characterization using X-ray diffraction and magnetic susceptibility measurements.
- Structural analysis at different temperatures to correlate with magnetic data.
Main Results:
- Two isomorphous, 2D layered coordination polymers, [Fe(tpmd)2(NCS)2]·5.5H2O (1) and [Fe(tpmd)2(NCSe)2]·7H2O (2), were successfully synthesized.
- Compound 1 displayed paramagnetic behavior, while compound 2 exhibited a two-step spin crossover transition around 145 K and 50 K.
- Structural analysis of compound 2 at 100 K revealed alternating layers with distinct iron(ii) coordination environments, consistent with mixed spin states.
Conclusions:
- The incorporation of NCSe- ligands in compound 2 is crucial for inducing spin crossover behavior.
- The observed two-step SCO in compound 2 is attributed to structural differences in the layered arrangement at low temperatures.
- These findings contribute to the design of functional coordination polymers with tunable magnetic properties.
Related Concept Videos
03:02Colors and Magnetism
12.4K
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...
12.4K
02:42Valence Bond Theory
9.7K
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...
9.7K
02:52Stereoisomerism
12.5K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
12.5K
02:34Structural Isomerism
19.8K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
19.8K
02:57Coordination Number and Geometry
16.8K
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.
16.8K
02:58Crystal Field Theory - Octahedral Complexes
28.1K
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...
28.1K