Related Experiment Video
Updated: Oct 5, 2026

Preparation of SNS Cobalt(II) Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
Structure-property relationships of a tetrapyrrolidinyl PNP-lariat ether and its complexes with potassium, sodium,
K Brandt1, P Seliger, A Grzejdziak
1Institute of Polymer Chemistry, Polish Academy of Science, 41-800 Zabrze, Poland.
Abstract:
Spectral properties of the tetrapyrrolidinyl PNP-lariat ether, L, and its complexes with K+, Na+, and Ag+ were investigated. Crystal structures of L and its complex with potassium iodide [KL]I were determined. Protonation constants of the ligand and formation constants of its complexes with Ag+, K+, and Na+ in aqueous solutions were determined. 1H NMR, 31P NMR, FTIR, and ESIMS spectra as well as potentiometric measurements indicate that complexation of Ag+ involves participation of the polyether oxygen donors and the endocyclic nitrogen atom of the cyclophosphazene ring. On the other hand, for complexation of K+ and Na+, only polyether oxygen atoms are involved. The latter conclusion is confirmed in the solid-state structure of the [KL]I complex.
Related Concept Videos
EDTA: Chemistry and Properties
Valence Bond Theory
Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Complexation Equilibria: The Chelate Effect
Formation of Complex Ions
Complexation Equilibria: Factors Influencing Stability of Complexes

