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09:44
Design, Synthesis, and Photochemical Properties of Clickable Caged Compounds
Published on: October 15, 2019
An unusually flexible expanded hexaamine cage and its Cu(II) complexes: variable coordination modes and incomplete
Chang-Jin Qin1, Lloyd James, Jy D Chartres
1Research School of Chemistry, Australian National University, Canberra ACT 0200, Australia.
Inorganic Chemistry
|August 3, 2011
Summary
The novel Me(8)tricosaneN(6) cage ligand stabilizes dynamic copper complexes, enabling pentacoordinate binding and a reversible Cu(II/I) redox couple. This contrasts with rigid sarcophagine complexes, highlighting the ligand
Area of Science:
- Coordination Chemistry
- Bioinorganic Chemistry
- Supramolecular Chemistry
Background:
- Bicyclic hexaamine cage ligands offer unique coordination environments for metal ions.
- The Me(8)tricosaneN(6) ligand possesses an expanded cavity compared to sarcophagine ligands.
- Copper(II) complexes with cage ligands are relevant in catalysis and biomimetic studies.
Purpose of the Study:
- To investigate the coordination behavior and structural diversity of copper(II) complexes with the Me(8)tricosaneN(6) ligand.
- To explore the solution dynamics and electrochemical properties of these complexes.
- To compare the coordination chemistry of Me(8)tricosaneN(6) with the sarcophagine ligand.
Main Methods:
- X-ray crystallography for structural determination of copper complexes.
- UV-Vis-NIR spectroscopy to study electronic transitions.
- Electron Paramagnetic Resonance (EPR) spectroscopy for electronic structure analysis.
- Cyclic voltammetry to assess redox properties.
Main Results:
- The Me(8)tricosaneN(6) ligand accommodates Cu(II) in both hexadentate and pentadentate coordination modes.
- Structural characterization of 6-coordinate [Cu(Me(8)tricosaneN(6))](ClO(4))(2) and 5-coordinate [Cu(Me(8)tricosaneN(6))](S(2)O(6)).
- A dynamic equilibrium between coordination modes in solution, favoring pentadentate square pyramidal geometry at neutral pH.
- Isolation and characterization of a protonated pentadentate complex [Cu(HMe(8)tricosaneN(6))](3+) at pH 1.
- Observation of a reversible Cu(II/I) redox couple for the pentacoordinate complex.
- Contrast with hexadentate sarcophagine copper(II) complexes, which do not stabilize Cu(I).
Conclusions:
- The expanded cavity of Me(8)tricosaneN(6) allows for flexible coordination and dynamic equilibria in copper complexes.
- Pentacoordinate copper complexes with Me(8)tricosaneN(6) exhibit unique structural, spectroscopic, and electrochemical properties.
- This ligand system offers new possibilities for stabilizing different metal oxidation states and coordination geometries.
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