Redox Activity of Noninnocent 2,2′-Bipyridine in Zinc Complexes: An Experimental and Theoretical Study

[Image: see text] We report on a systematical reactivity study of β-diketiminate zinc complexes with redox-active 2,2′-bipyridine (bpy). The reaction of LZnI (L = HC[C(Me)N(2,6-iPr(2)C(6)H(3))](2)) with NaB(C(6)F(5))(4) in the presence of bpy yielded [LZn(bpy)][B(C(6)F(5))(4)] (1), with bpy serving as a neutral ligand, whereas reduction reactions of LZnI with 1 or 2 equiv of KC(8) in the presence of bpy gave the radical complex LZn(bpy) (2) and [2.2.2-Cryptand-K][LZn(bpy)] (3), in which bpy either acts as a π-radical anion or a diamagnetic dianion, respectively. The paramagnetic nature of 2 was confirmed via solution magnetic susceptibility measurements, and UV–vis spectroscopy shows that 2 exhibits absorption bands typical for bpy radical species. The EPR spectra of 2 and its deuterated analog 2-d(8) demonstrate that the spin density is localized to the bpy ligand. Density functional theoretical calculations and natural bond orbital analysis were employed to elucidate the electronic structure of complexes 1–3 and accurately reproduced the structural experimental data. It is shown that reduction of the bpy moiety results in a decrease in the β-diketiminate co-ligand bite angle and elongation of the Zn–N(β-diketiminate) bonds, which act cooperatively and in synergy with the bpy ligand by decreasing Zn–N(bpy) bond lengths to stabilize the energy of the LUMO.