The reaction Co(H ₂ O) ₆ ²⁺ + H ₂ O ₂ proceeds via a transient that decomposes into Co ^II (H ₂ O)(OOH)(OH) ₂ + CO ₃ ˙ ⁻ . Plausible biological implications are pointed out.

Co(II) complexes and Co(H₂O)₆ ²⁺ are used as catalysts in advanced oxidation processes. Therefore it was decided to study the kinetics of reaction of Co(H₂O)₆ ²⁺ with H₂O₂. Surprisingly, the kinetic results point out that the process involves three consecutive reactions, each of them requiring an H₂O₂ molecule, i.e. three H₂O₂ molecules ligate to the central cobalt cation prior to the formation of radicals. DFT analysis suggests that the transient (H₂O)₃Co^II(OOH)₂(H₂O₂) decomposes via: (H₂O)₃Co^II(OOH)₂(H₂O₂) → (H₂O)₃Co^II(OOH)(˙OOH)(OH) + ˙OH ΔG⁰ = −5.975 kcal mol⁻¹, with no evidence for the formation of a Co(III) transient. It is proposed that analogous mechanisms are involved whenever the redox potential of the central cation is too high to enable the reaction: M(H₂O)₆ ⁿ⁺ + H₂O₂ → M⁽ⁿ⁺¹⁾⁺ _aq + ˙OH + OH⁻.

NiL _i ²⁺ are good electro-catalysts for water oxidation in phosphate/carbonate buffers. The active species are L(X)Ni ^IV OH ^{4−(3−n+1)/(2−n+1)} . Carbonate behaves differently from phosphate.

Sulfated polysaccharides produced by microalgae, which are known to exhibit various biological activities, may potentially serve as natural antioxidant sources. To date, only a few studies have examined the antioxidant bioactivity of red microalgal polysaccharides. In this research, the effect of different salts on the antioxidant activities of two red microalgal sulfated polysaccharides derived from Porphyridium sp. and Porphyridium aerugineum were studied in a soy bean-based infant milk formula. Salt composition and concentration were both shown to affect the polysaccharides’ antioxidant activity. It can be postulated that the salt ions intefer with the polysaccharide chains’ interactions and alter their structure, leading to a new three-dimensional structure that better exposes antiooxidant sites in comparison to the polysaccharide without salt supplement. Among the cations that were studied, Ca²⁺ had the strongest enhancement effect on antioxidant activities of both polysaccharides. Understanding the effect of salts on polysaccharides’ stucture, in addition to furthering knowledge on polysaccharide bioactivities, may also shed light on the position of the antioxidant active sites.

We use dip-pen nanolithography to accurately pattern Ni(OH)₂ nanoclusters on a metachemical surface with an exceptionally large surface area. The distance between the nanoclusters can be manipulated to control the oxygen-evolution reaction current and overpotential, thereby improving the efficiency of the water-splitting process while using minute amounts of the catalyst.