Related Experiment Video
Updated: Jul 10, 2026
Preparation of SNS Cobalt(II) Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
Archetypical modeling and amphiphilic behavior of cobalt(II)-containing soft-materials with asymmetric tridentate
Rajendra Shakya1, Sarmad Sahiel Hindo, Libo Wu
1Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
Abstract:
The stabilization of a bivalent oxidation state in cobalt complexes of phenolate-based asymmetric tridentate ligands with iodo and bromo substituents is studied. The complexes [CoII(LIA)2].2CH3OH (1) and [CoII(LBrA)2].CH3OH (2) were characterized by means of several spectroscopic and spectrometric techniques. The molecular structure of 1 was determined by diffractometric analysis and reveals the cobalt(II) ion in a distorted-octahedral geometry. The centrosymmetric metal ion adopts a local D2h symmetry and is surrounded by facially coordinated ligands. Equivalent donor sets in both ligands are trans to each other, and DFT calculations suggest that the fac-trans configuration is favored by a small margin when compared to the fac-cis isomers. Both DFT calculations and EPR spectroscopy agree with a high-spin S=3/2 electronic configuration given by [ag1, b1g1, ag1, b2g2, b3g2]. This oxidation state was indirectly observed by the lack of a ppiphenolate-->dsigma*cobalt(III) charge-transfer band, which is found between 430 and 470 nm for similar cobalt(III) species. On the basis of the geometrical preferences and the oxidation state of archetypical 1 and 2, two metallosurfactants [CoII(LI-ODA)2] (3) and [CoII(LI-NOBA)2].CH2Cl2 (4) were obtained. The redox chemistry of 1-4 is marked by metal- and ligand-centered activity with several follow up processes and film formation on the electrode. Both metallosurfactants exhibit amphiphilic properties and organization, as shown by compression isotherms and Brewster angle microscopy but exhibit dissimilar collapse mechanisms; whereas 3 collapses at constant pressure, 4 exhibits a constant-area collapse. Langmuir-Blodgett films are readily obtained and were characterized by equilibrium contact angle and atomic force microscopy.
Related Concept Videos
02:42Valence Bond Theory
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...
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.
02:34Structural 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...
00:43Complexometric Titration: Ligands