Heteroleptic copper phenanthroline complexes in motion: From stand-alone devices to multi-component machinery

Abstract

a b s t r a c tTwo and a half decades of copper phenanthroline-based switches, devices and machines have illustrated the rich dynamic nature of these metal complexes. With an emphasis on the metal-ligand dissociation as the rate-determining step the present review summarizes not only spectacular examples of machinery, but also highlights rate data collected during a variety of investigations. Copper-ligand exchange reactions are mostly triggered by redox processes, addition of metal ions or addition of ligands. While the rate data spread over >8 orders of magnitude, individual effects of solvent, steric bulk, flexibility, r-basicity and the trajectory (intra-vs. intermolecular dissociation) have large impact. Unfortunately, in many cases the exact mechanism in the rate-determining step (nucleophile-induced vs. monomolecular metal-ligand dissociation) has not been determined, suggesting to invest further efforts in the physical (in)organic chemistry of such coordination-driven systems.

Double Rotors with Fluxional Axles: Domino Rotation and Azide–Alkyne Huisgen Cycloaddition Catalysis

“…The activation data were determined as Δ H ≠ =51.1±0.7 kJ mol −1 , Δ S ≠ =25.5±3.0 J mol −1 K −1 , and Δ G ≠ 298 =43.5 kJ mol −1 (Supporting Information, Figure S24). Since the kinetic data for exchange in [Cu 4 ( A ) 2 ] 4+ are very similar to those of previously reported nanorotors that operate via single N py →[Cu(phenAr 2 )] + dissociation (Δ G ≠ 298 =46.6 kJ mol −1 ), there is convincing evidence that only one HETPYP interaction is cleaved at any given time in [Cu 4 ( A ) 2 ] 4+ . Hence, the mechanism of exchange seems to follow an intramolecular nondirectional rotation involving two axles with dissociation of one N py →[Cu(phenAr 2 )] + interaction being the rate‐limiting step.…”

Doppelrotoren mit fluktuierenden Achsen: Domino‐Rotation und Katalyse der Azid‐Alkin‐Huisgen‐Cycloaddition

“…Die Aktivierungsdaten wurden bestimmt als Δ H ≠ =51.1±0.7 kJ mol −1 , Δ S ≠ =25.5±3.0 J mol −1 K −1 und Δ G ≠ 298 =43.5 kJ mol −1 (Hintergrundinformationen, Abbildung S24). Da die kinetischen Daten für den Austausch in [Cu 4 ( A ) 2 ] 4+ sehr ähnlich denen der zuvor berichteten Nanomotoren sind, die über eine einzige N py →[Cu(phenAr 2 )] + ‐Dissoziation arbeiten, gibt es überzeugende Belege dafür, dass in [Cu 4 ( A ) 2 ] 4+ immer nur eine HETPYP‐Interaktion zu einem bestimmten Zeitpunkt gespalten wird. Folglich scheint der Austauschmechanismus einer intramolekularen, ungerichteten Rotation zu folgen, die zwei Achsen umfasst, wobei die Dissoziation einer N py →[Cu(phenAr 2 )] + ‐Wechselwirkung der geschwindigkeitsbestimmende Schritt ist.…”

Physicochemical Insight into Coordination Systems Obtained from Copper(II) Bromoacetate and 1,10-Phenanthroline

“…The copper usually exists in the form of Cu + and Cu 2+ cations, but species such as Cu 3+ and Cu 4+ also exist [ 9 , 10 ]. Each can adopt a whole variety of coordination polyhedra [ 11 , 12 , 13 , 14 ]. Even small changes in the structure of a coordination unit may significantly influence the physicochemical properties of a compound.…”