Coordination of 1,10-phenanthroline and 2,2′-bipyridine to Li ~+ in different ionic liquids. how innocent are ionic liquids?

摘要

On the basis of ~7Li NMR measurements, we have made detailed studies on the influence of the ionic liquids [emim][NTf_2], [emim][ClO_4], and [emim][EtSO_4] on the complexation of Li~+ by the bidentate N-donor ligands 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen). For each of the employed ionic liquids the NMR data implicate the formation of [Li(bipy)_2]~+ and [Li(phen)_2]~+, respectively. X-ray diffraction studies were performed to determine the coordination pattern in the solid state. In the case of [emim][ClO_4] and [emim][EtSO_4], crystal structures confirmed the NMR data, resulting in the complexes [Li(bipy)_2ClO _4] and [Li(phen)_2EtSO_4], respectively. On the contrary, the ionic liquid [emim][NTf_2] generated the Ci symmetric, dinuclear, supramolecular cluster [Li(bipy)(NTf_2)] _2, where the individual Li~+ centers were found to be bridged by two [NTf_2] anions. Density functional theory (DFT)-calculations lead to further information on the effect of stacking on the coordination geometry of the Li~+ centers.