The perils and opportunities of reactive building blocks: Attempted synthesis of new Hg(CN)2-based coordination polymers and the structures of the resulting products

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.

Unusual N-oxide formation in the peroxidation of cobalt(ii) ethylenediaminetetraacetates

Unlike the usual formations of peroxo and superoxo cobalt products as oxygen carriers, N-oxido cobalt(ii) ethylenediaminetetraacetates K₄[Co₂(edtaO₂)₂]·nH₂O [n = 6.5 (1), 10 (2), H₄edta = ethylenediaminetetraacetic acid, C₁₀H₁₆O₈N₂] and their aggregate [Co₂(edtaO₂)(H₂O)₆]_n·2nH₂O (3) were obtained as dioxygen insertion products. The cobalt ions in dimers 1 and 2 are hexa-coordinated by two edtaO₂ ligands in different configurations respectively, which is attributed to the packing of an interesting (H₂O)₁₂ water cluster in 2. Further reaction of K₄[Co₂(edtaO₂)₂]·nH₂O with hydrogen peroxide results in the final trivalent cobalt ethylenediaminetetraacetate K[Co(edta)]·2H₂O (4). A water-soluble coordination polymer Na_2n[Co(edta)]_n·4nH₂O (5) was also obtained with a one dimensional zigzag structure. Bond valence calculation is consistent with the products 1-5.

A family of [Ni8] cages templated by μ6-peroxide from dioxygen activation

[Ni₈] cages templated by η³:η³:μ₆-O₂²⁻ from O₂ activation: the ligand found oxidized within the cages.