A Remarkable ParaCEST Activity Shown by a Co(II) Complex of Bis-Dipicolinamideacetamide With One Inner Sphere Water
Soumyadarshi Rath1, Suvam Kumar Panda1, Anupriya Chattapadhya2,3
1School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, 752050, India.
Chemistry, an Asian Journal
|February 1, 2025
Summary
The cobalt(II)-bis-dipicolinamideacetamide (BDPAA) complex shows significant paraCEST activity, unlike its iron and nickel counterparts. This activity, attributed to exchangeable carboxamide protons, is optimal around physiological pH.
Area of Science:
- Coordination Chemistry
- Supramolecular Chemistry
- Biophysical Chemistry
Background:
- Paramagnetic chemical exchange saturation transfer (paraCEST) imaging offers a novel approach for molecular imaging.
- Developing novel contrast agents with tunable properties is crucial for advancing paraCEST applications.
Purpose of the Study:
- To synthesize and characterize novel metal complexes with a pyridine-based tri(carboxamide) ligand (BDPAA).
- To investigate the paraCEST properties of iron, cobalt, and nickel complexes of BDPAA.
- To elucidate the structural and electronic factors governing paraCEST activity.
Main Methods:
- Synthesis of Fe(II), Co(II), and Ni(II) complexes with BDPAA ligand.
- Solid-state structural analysis using single-crystal X-ray diffraction.
- Solution-state paraCEST studies using 1H NMR spectroscopy.
- Determination of proton exchange rate constants.
Main Results:
- The cobalt(II)-BDPAA complex exhibited significant paraCEST activity, while iron and nickel complexes showed minimal to no activity.
- Single crystal X-ray analysis revealed a distorted pentagonal bipyramidal geometry for the cobalt complex.
- Optimal paraCEST effect for the Co-BDPAA complex was observed at physiological pH (7.4-7.6).
Conclusions:
- The exchangeable carboxamide NH2 protons of the BDPAA ligand are key to the observed paraCEST activity in the cobalt complex.
- The Co(II)-BDPAA complex demonstrates potential as a paraCEST contrast agent.
- Structural and electronic properties significantly influence paraCEST performance.
More Related Videos
Related Concept Videos
02:42Valence Bond Theory
8.4K
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...
8.4K
03:45Formation of Complex Ions
23.2K
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
23.2K
02:34Structural Isomerism
19.1K
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...
19.1K
03:13Intermolecular Forces
57.5K
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen...
57.5K
02:35Noncovalent Attractions in Biomolecules
47.7K
Noncovalent attractions are associations within and between molecules that influence the shape and structural stability of complexes. These interactions differ from covalent bonding in that they do not involve sharing of electrons.
Four types of noncovalent interactions are hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions.
Hydrogen bonding results from the electrostatic attraction of a hydrogen atom covalently bonded to a strong-electronegative atom like oxygen,...
Four types of noncovalent interactions are hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions.
Hydrogen bonding results from the electrostatic attraction of a hydrogen atom covalently bonded to a strong-electronegative atom like oxygen,...
47.7K
03:02Colors and Magnetism
11.5K
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...
11.5K