Electronic structure of binuclear mixed valence copper azacryptates derived from integrated advanced EPR and DFT...

Area of Science:

• Coordination Chemistry
• Bioinorganic Chemistry
• Spectroscopy

Background:

• Binuclear copper complexes with mixed valence states are rare.
• These complexes serve as models for the Cu(A) site in enzymes like nitrous oxide reductase and cytochrome c oxidase.
• Azacryptand ligands provide stability for these unique copper complexes.

Purpose of the Study:

• To synthesize and characterize binuclear, mixed valence copper complexes.
• To investigate the electronic and spatial structures of these complexes in frozen solution.
• To compare experimental magnetic data with density functional theory (DFT) calculations.

Main Methods:

• Synthesis of binuclear copper complexes stabilized by azacryptand ligands.
• Magnetic interaction measurements including g-tensor and hyperfine couplings (Cu, N, H).
• Advanced Electron Paramagnetic Resonance (EPR) techniques: CW-EPR, pulsed ENDOR, 2D TRIPLE, HYSCORE.
• Density Functional Theory (DFT) calculations for structural and electronic analysis.

Main Results:

• The unpaired electron is equally delocalized over the two copper ions in the [Cu(+1.5), Cu(+1.5)] state.
• Experimental magnetic data (g-tensor, hyperfine couplings) align well with DFT predictions.
• DFT calculations aided in simulating and assigning complex ENDOR spectra for N and H nuclei.

Conclusions:

• The study successfully characterized the structure of binuclear copper complexes in frozen solution.
• The findings validate the use of DFT in conjunction with advanced EPR techniques for studying such systems.
• These complexes represent valuable synthetic models for understanding electron transfer mechanisms in metalloenzymes.