Formation of a Bridged Butterfly-Type μ-η²:η²-Peroxo Dicopper Core Structure with a Carboxylate Group

Abstract

The µ-η 2 :η 2 -peroxodicopper(II) (Cu 2 (µ-η 2 :η 2 -O 2 )) and bis(µoxo)dicopper(III) (Cu 2 (µ-O) 2 ) species have been investigated in the model studies of type III copper proteins, and these structures are also considered as important motifs for O 2 -activating metalloproteins in biological systems. 1,2 The interconversion between these species in solution was found to depend on organic solvents and counteranions. 2,3 Recent studies of the interconversion equilibrium in copper-aliphatic diamine complex systems strongly suggested that coordination of counteranions promotes the conversion of Cu 2 (µ-O) 2 to Cu 2 (µ-η 2 :η 2 -O 2 ) species. 2b,3b,c However, direct evidence for formation of the anion-coordinating structure is yet to be presented. Here, we report the formation and crystal structure of a new Cu 2 (µ-η 2 :η 2 -O 2 ) complex with a bridging carboxylate ligand. 4a Structural studies and density functional theory (DFT) calculations suggested factors regulating stepwise-activation of dioxygen by bridging-carboxylate ligation to the dicopper core.

Acid/base triggered interconversion of μ-η2:η2-peroxido and bis(μ-oxido) dicopper intermediates capped by proton-responsive ligands

“…Å ( P 5 ) are typical for P cores, the bridging peroxido ligands exhibit the largest bond lengths ( P 4 : 1.56 Å, P 5 : 1.58 Å) reported so far for synthetic and biological Cu(μ-η 2 :η 2 -O 2 )Cu systems (Table S3† presents a compilation of geometric and spectroscopic features of all literature-known μ-η 2 :η 2 -peroxidodicopper( ii ) species). 33–38 Most of the metric parameters of P 4 and P 5 are in excellent agreement with those derived from Cu K-edge extended X-ray absorption fine structure (EXAFS) data, for the corresponding P cores obtained with the capping ligands t Bu,H BOX ( t Bu,H P ) and H,H BOX ( H,H P ). 29 …”

Relation between the Catalytic Efficiency of the Synthetic Analogues of Catechol Oxidase with Their Electrochemical Property in the Free State and Substrate-Bound State

“…Conversely, it is remarkable that the geometry of the (μ 2 -benzoato)-(μ 2 -peroxo)-bis(α-isosparteine)-dicopper (QOSRAS) 40 structure is similar to the optimized geometry of intermediate D (see Figure 8, bottom right) concerning bond distances and angles, keeping in mind that the two copper centers are bridged by a carboxylate instead of phenolate (the Cu−O 2 unit is less butterfly distorted).…”

X-ray absorption spectroscopic characterization of the diferric-peroxo intermediate of human deoxyhypusine hydroxylase in the presence of its substrate eIF5a

“…Importantly, both the ( μ - η 2 : η 2 -peroxo)diiron(III) moiety and the open-core isomer of the bis( μ -oxo)diiron(IV) diamond core, respectively proposed in Scheme 3 C & D, would fit within the Fe•••Fe distance constraints of the hDOHH active site. Although synthetic complexes with ( μ - η 2 : η 2 -peroxo)diiron(III) cores have yet to be described, corresponding dicopper complexes are well known and exhibit Cu•••Cu distances of 3.6 Å for those with planar Cu 2 O 2 units [112–114]; in one example, the Cu•••Cu distance can be decreased by conversion to a nonplanar butterfly configuration [115]. On the other hand, there are two precedents for the open-core formulation among synthetic high-valent diiron complexes which have been shown to have respective Fe•••Fe distances of 3.3 and 3.6 Å [116, 117].…”