Structure, EPR/ENDOR and DFT characterisation of a [Cu(II)(en)2](OTf)2 complex.

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Spectroscopy

Background:

• Jahn-Teller distortion in copper(II) complexes can influence their structural and electronic properties.
• Understanding the coordination environment and electronic structure of copper(II) complexes is crucial for various applications.

Purpose of the Study:

• To synthesize and characterize the Jahn-Teller distorted copper(II) complex, [Cu(en)2](OTf)2.
• To elucidate the structural and electronic properties of the complex using a combination of experimental and computational methods.
• To investigate the correlation between nitrogen hybridization and hyperfine coupling in copper(II) systems.

Main Methods:

• X-ray crystallography for solid-state structure determination.
• Electron Paramagnetic Resonance (EPR) and Electron Nuclear Double Resonance (ENDOR) spectroscopy for spin Hamiltonian parameter determination.
• Density Functional Theory (DFT) calculations for theoretical validation.

Main Results:

• The crystal structure revealed an intra- and inter-molecular hydrogen-bonded network involving N-H groups and triflate anions.
• EPR/ENDOR determined spin Hamiltonian parameters showed excellent agreement with DFT calculations.
• Angular selective ENDOR confirmed the structure in frozen solution, consistent with crystal structure and indicating axial counter-ion coordination.
• Small (14)N superhyperfine couplings indicated sp(3) hybridization of coordinating nitrogens.

Conclusions:

• The study successfully characterized the Jahn-Teller distorted copper(II) complex.
• The combined spectroscopic and computational approach provided a comprehensive understanding of the complex's structure and electronic properties.
• The correlation between (14)N hyperfine coupling and nitrogen hybridization serves as a valuable tool for determining coordination and donor nature in unknown copper(II) systems.