Structural characteristics of redox-active pyridine-1,6-diimine complexes: Electronic structures and ligand oxidation levels

Effect of PDI ligand binding pattern on the electrocatalytic activity of two Ru(II) complexes for CO2 reduction

“…As depicted in Figure a, complex 1 displays five successive reduction peaks at E pc = −0.84, −1.06, −1.16, −1.56, and −1.89 V in MeCN solution, while the peak current at −1.31 V is likely the superimposed current . According to the results of the DFT calculations in our previous research, the lowest unoccupied molecular orbital (LUMO) of complex 1 is primarily located on the PDI ligand backbone, thus the first three irreversible reduction processes could be PDI anti π‐orbital based, leading to the formation of a trianionic radical (PDI • ) 3− . The first two reduction potentials are lower than that of the other reported PDI complexes, which may due to the effect of the strong π‐donors of the two triphenylphosphine ligands .…”

“…[72] According to the results of the DFT calculations in our previous research, [66] the lowest unoccupied molecular orbital (LUMO) of complex 1 is primarily located on the PDI ligand backbone, thus the first three irreversible reduction processes could be PDI anti π-orbital based, leading to the formation of a trianionic radical (PDI • ) 3− . [29] The first two reduction potentials are lower than that of the other reported PDI complexes, which may due to the effect of the strong π- donors of the two triphenylphosphine ligands. [55,73] The last two peak currents at −1.56 and −1.89 V could be attributed to the Ru II /Ru I and Ru I /Ru 0 redox couples, respectively.…”

“…Thus, in order to enhance the reactivity and selectivity of electrocatalysts for CO 2 reduction, considerable efforts have been devoted to coupling the electrocatalytic process to the synergistic catalytic effect between central metal ions and various ligands. Redox active ligands, first described as “non‐innocent ligands”, have performed a systematic study of such ligands. They have proved to be valuable in the development of efficient catalysts due to their unique capabilities of reserving electrons to assist metal complexes in multiple‐electron transformations and modifying the electronic properties or Lewis acidity of the central metal ions, etc .…”

Ruthenium (II) complexes bearing thioether‐appended α‐iminopyridine ligands: Arene precursors permit access to κ2‐N,N and κ3‐N,N,S complexes

“…Several highly‐active catalyst systems derived from di(imine) or α‐imino(pyridine) have been reported in recent years . Wieghardt and co‐workers have demonstrated that the presence of a redox‐innocent donor arm does not negate the activity of redox‐active α‐imino(pyridine) ligand frameworks . With these properties in mind, we sought to identify a series of ligands featuring a potentially redox‐active moiety and a thioether donor, capable of selectively dechelating from the metal center.…”

“…[22][23][24][25][26][27][28] Wieghardt and co-workers have demonstrated that the presence of a redox-innocent donor arm does not negate the activity of redox-active α-imino(pyridine) ligand frameworks. [13,15,[29][30][31] With these properties in mind, we sought to identify a series of ligands featuring a potentially redox-active moiety and a thioether donor, capable of selectively dechelating from the metal center. We imagine these species as useful precatalysts for a variety of transformations, and hoped to learn more about the solution chemistry of such complexes in order to better understand the origin of such catalyst activity.…”