Complexation kinetics of copper(II) and nickel(II) with macrocycles: identification of an outer-sphere chelate effect
Nichola McCann1, Geoffrey A Lawrance, Yorck-Michael Neuhold
1University of Newcastle, Newcastle NSW 2308, Australia.
Abstract:
Ligand-protonation constants and complexation kinetics of differently protonated forms of 10-methyl-1,4,8,12-tetraazacyclopentadecan-10-amine, 1,4,8,12-tetraazacyclopentadecane, and 1,4,8,12-tetraazacyclopentadecan-10-carboxylic acid with Cu(II) and Ni(II) in aqueous solution have been determined. These results are combined with a wide range of published complexation rate constants of partially protonated macrocyclic ligands with the same metal ions. Insight is gained into the electrostatic effects and the outer-sphere interaction of partially protonated ligands with aquated metal ions. An outer-sphere chelate effect has been ascertained.
Related Concept Videos
Complexation Equilibria: The Chelate Effect
Extraction: Advanced Methods
Formation of Complex Ions
Complexation Equilibria: Factors Influencing Stability of Complexes
Complexation Equilibria: Overview
The equilibrium constant of the complexation reaction is represented as the formation constant...
Colors 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.


