Related Experiment Video
Updated: May 10, 2026
07:24
Paramagnetic Relaxation Enhancement for Detecting and Characterizing Self-Associations of Intrinsically Disordered Proteins
Published on: September 23, 2021
Spin state modulation of iron spin crossover complexes via hydrogen-bonding self-assembly
Michael C Young1, Erica Liew, Jonathan Ashby
1Department of Chemistry, University of California - Riverside, 501 Big Springs Rd., Riverside, CA 92521, USA.
Chemical Communications (Cambridge, England)
|June 8, 2013
Summary
Researchers developed a new method using hydrogen bonding to control the spin crossover behavior of iron complexes. This technique allows for the modulation of spin states in solution, a first for this type of self-assembly.
Area of Science:
- Coordination Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Spin crossover (SCO) is a phenomenon in some metal complexes where the spin state changes in response to external stimuli.
- 2,2'-bipyridine ligands are commonly used in coordination chemistry to form metal complexes with interesting properties.
- Self-assembly driven by hydrogen bonding is a powerful tool for creating ordered supramolecular structures.
Purpose of the Study:
- To investigate the spin crossover behavior of iron complexes based on 6-diaminotriazyl-2,2'-bipyridines.
- To explore the use of hydrogen bonding-mediated self-assembly to modulate the spin crossover properties.
- To demonstrate the first instance of solution-phase self-assembly controlling spin state modulation.
Main Methods:
- Synthesis of iron complexes incorporating 6-diaminotriazyl-2,2'-bipyridine ligands.
- Co-crystallization and solution-phase studies involving barbiturate partners to induce hydrogen bonding.
- Characterization of spin crossover behavior using techniques such as variable-temperature magnetic susceptibility measurements.
Main Results:
- The synthesized iron complexes exhibit spin crossover behavior.
- Hydrogen bonding interactions with a barbiturate partner successfully modulated the spin crossover from a mixed spin state to a high-spin state.
- This modulation was achieved through solution-phase self-assembly, highlighting the system's responsiveness.
Conclusions:
- Iron complexes with 6-diaminotriazyl-2,2'-bipyridines are capable of spin crossover.
- Solution-phase self-assembly, driven by specific hydrogen bonding interactions, can effectively tune the spin state of these iron complexes.
- This work represents a novel approach to controlling spin crossover phenomena using supramolecular self-assembly.
More Related Videos
Related Concept Videos
01:17Spin–Spin Coupling: One-Bond Coupling
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
02:42Valence Bond Theory
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...
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
03:02Colors and Magnetism
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 eye.
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 eye.
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
01:08Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...