RuIII(EDTA) mediated activation of redox signalling molecules

Utilization of Low-Concentration CO2 with Molecular Catalysts Assisted by CO2-Capturing Ability of Catalysts, Additives, or Reaction Media

Increasing concentration of atmospheric CO₂ is a worldwide concern and continues to trigger various environmental problems. Photo- or electrocatalytic CO₂ reduction (CO₂-Red) using solar energy, i.e., artificial photosynthesis, is a prospective technique owing to its sustainability and the usefulness of the reaction products. Concentrations of CO₂ in exhaust gases from industries are several % to 20%, and that in the atmosphere is about 400 ppm. Although condensation processes of CO₂ require high energy consumption and cost, pure CO₂ has been used in most of the reported studies for photo- and electrocatalytic CO₂-Red because the reaction between CO₂ and the catalyst could be one of the rate-limiting steps. To address these issues and provide a repository of potential techniques for other researchers, this perspective summarizes the catalytic systems reported for the reduction of low-concentration CO₂, which utilize a combination of catalytic CO₂-Red and CO₂-capturing reactions (or CO₂ adsorption). First, we describe CO₂ insertions into M-X bonds of the catalysts, which increase the rate constants and/or equilibrium constants for CO₂ binding on the catalysts, and modifications of the second coordination sphere to stabilize the CO₂-bound catalysts. Furthermore, we discuss the reaction media used for catalytic CO₂-Red that have the unique effect of increasing CO₂ concentrations around the catalysts. These reaction media include typical CO₂-capturing additives, ionic liquids, and metal-organic frameworks.

RuIII(edta)-mediated interaction of nitrite and sulphide: formation of an N-bonded thionitrous acid (HSNO) complex of RuIII(edta) in aqueous solution

It is reported for the first time that [Ru^III(edta)(NO⁺)] (edta⁴⁻ = ethylenediaminetetraacetate) generated from [Ru^III(edta)(NO₂)]²⁻ at lower pH (∼3.5) can react with NaHS to form the thionitrous acid bound Ru(edta) complex in aqueous solution.