Electrochemical behavior and dioxygen reactivity of tripodal dinuclear copper complexes linked by unsaturated rigid spacers

Abstract

New dinucleating ligands based on two tripodal tris(2-pyridylmethyl)amine (TMPA) units linked by a series of delocalized π-electrons spacers have been synthesized. Their di-Cu(II) complexes have been prepared and structurally characterized. As compared to the corresponding monotopic complexes, these dinuclear Cu(II) complexes reveal spectroscopic and voltammetric features ascribable to weakly perturbed electronic interactions. In the case of the anthracenyl spacer, observation both in the solid and in solution suggests that the existence of intramolecular π-π stacking interactions influences the geometry of the complex and hence its electronic properties. The bis-Cu(I) complexes were prepared electrochemically. In the specific case of the complex bearing a mono-alkyne spacer, addition of dioxygen in acetonitrile leads to the slow formation of a trans-μ-1,2 peroxo Cu(2) complex which shows good stability at 268 K (t(1/2) = 240 s). Analysis of the kinetics of the peroxo formation by UV-vis spectroscopy suggests that the increased activation barrier for intramolecular binding of dioxygen is due to the rigidity of the spacer.

Mechanistic Investigations into the Selective Reduction of Oxygen by a Multicopper Oxidase T3 Site-Inspired Dicopper Complex

“…Moreover, the catalytic activity of these complexes has often been investigated in organic solvents and chemical reducing agents are typically used. 25 − 29 These reaction conditions do not resemble those in which the ORR activity of MCOs has been studied.…”

“…However, when it comes to the ORR reactivity, only a few complexes with multiple metal centers have been investigated to date. Moreover, the catalytic activity of these complexes has often been investigated in organic solvents and chemical reducing agents are typically used. − These reaction conditions do not resemble those in which the ORR activity of MCOs has been studied.…”

Reactivity Differences for the Oxidation of FeIIFeII to FeIII(µ‐O)FeIII Complexes Caused by Pyridyl versus 6‐Methyl‐Pyridyl Ligands

“…The ligand tpa [= tris(2‐pyridylmethyl)amine] and various substituted derivates (Schemeà) were employed to stabilize high‐valent dinuclear iron complexes and to study their reactivities . Also dinucleating ligand derivatives have been developed for this purpose …”

Oxidative ligand cleavage in a copper(II) complex containing aniline moiety induced by copper(II) perchlorate in acetonitrile

“…The color is not corresponding the original ligand atpa (yellow), Cu(ClO 4 ) 2 (blue) nor [Cu( atpa )] 2+ (blue‐green). The Cu(II) complexes with amine‐based ligand, for example, dipicolyl amine and tripodal amine coordinating ligand normally demonstrated blue to green color (absorbance around 600–900 nm depending on geometric pattern of the Cu center) 20 …”