Electronic and Geometric Structures of Paramagnetic Diazadiene Complexes of Lithium and Sodium.

The electronic and molecular structures of the lithium and sodium complexes of 1,4-bis(2,6-diisopropylphenyl)-2,3-dimethyl-1,4-diazabutadiene ( ^Me2 DAD ^Dipp ) were fully characterized by using a multi-frequency electron paramagnetic resonance (EPR) spectroscopy approach and crystallography, together with density functional theory (DFT) calculations. EPR measurements, using T ₁ relaxation-time-filtered pulse EPR spectroscopy, revealed the diagonal elements of the A and g tensors for the metal and ligand sites. It was found that the central metals in the lithium complexes had sizable contributions to the SOMO, whereas this contribution was less strongly observed for the sodium complex. Such strong contributions were attributed to structural specifications (e.g. geometrical data and atomic size) rather than electronic effects.