Related Experiment Video
Updated: Jun 20, 2026
Preparation of SNS Cobalt(II) Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
Structural and magnetic variability of cobalt(II) complexes with bridging pyrazolate ligands bearing appended imine
Anna Sachse1, Serhiy Demeshko, Franc Meyer
1Institut für Anorganische Chemie, Georg-August-Universität Göttingen, 37073, Göttingen, Germany. franc.meyer@chemie.uni-goettingen.de
Abstract:
The synthesis of new binucleating pyrazole-derived ligands (HL2, HL3) with bulky 2,6-diisopropylphenylimine side arms and backbone phenyl groups at the pyrazole-C4 and/or at the imine-C, which are derivatives from the known ligand HL1, is reported. Crystallographic analyses of three cobalt(II) complexes coordinated by ligands [L1-3]- reveal distinct metal to ligand ratios and different structural motifs in the solid state: [L1Co2Cl3(H2O)2(EtOH)] (1), [(L2)3Co4Cl5] (2), or [(L3)2Co4Cl6(H2O)5] (3). Metal ions are five-coordinate in 1, four- and six-coordiante in 2, and six-coordinate in 3. UV-Vis spectroscopy and ESI mass spectrometry suggest that complexes 2 and 3 retain their structures also in solution, whereas 1 partially dimerizes and is in equilibrium with tetrametallic species akin to 3. Magnetic susceptibility measurements indicate weak to moderate antiferromagnetic coupling between five-coordinate or between six-coordinate cobalt(II) ions, but weak ferromagnetic coupling between four- and six-coordinate cobalt(II).
More Related Videos
Related Concept Videos
02:34Structural Isomerism
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 be...
02:42Valence Bond Theory
03:02Colors and Magnetism
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.
02:58Crystal Field Theory - Octahedral Complexes
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...
02:51Metal-Ligand Bonds
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...
02:57Coordination Number and Geometry