CO ₂ conversion to small bio-molecules on greigite minerals under room temperature and pressure.

A new low‐energy pathway is reported for the electrochemical reduction of CO₂ to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P₆₆₆₁₄][124Triz] is able to chemisorb CO₂ through equimolar binding of CO₂ with the 1,2,4‐triazole anion. This chemisorbed CO₂ can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO₂ within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P₆₆₆₁₄][NTf₂]) undergoes reduction at significantly increased overpotentials, producing only CO as the product.

The sensing and differentiation of explosive molecules is key for both security and environmental monitoring. Single fluorophores are a widely used tool for explosives detection, but a fluorescent array is a more powerful tool for detecting and differentiating such molecules. By combining array elements into a single multichannel platform, faster results can be obtained from smaller amounts of sample. Here, five explosives are detected and differentiated using quantum dots as luminescent probes in a multichannel platform: 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), tetryl (2,4,6-trinitrophenylmethylnitramine), cyclotrimethylenetrinitramine (RDX), and pentaerythritol tetranitrate (PETN). The sharp, variable emissions of the quantum dots, from a single excitation wavelength, make them ideal for such a system. Each color quantum dot is functionalized with a different surface receptor via a facile ligation process. These receptors undergo nonspecific interactions with the explosives, inducing variable fluorescence quenching of the quantum dots. Pattern analysis of the fluorescence quenching data allows for explosive detection and identification with limits-of-detection in the ppb range.

Reactions of Fe₂(CO)₆(μ-pdt) (pdt = SCH₂CH₂CH₂S) with aminodiphosphines Ph₂PN(R)PPh₂ (R = allyl, ⁱPr, ⁱBu, p-tolyl, H) have been carried out under different conditions. At room temperature in MeCN with added Me₃NO·2H₂O, dibasal chelate complexes Fe₂(CO)₄{κ²-Ph₂PN(R)PPh₂}(μ-pdt) are formed, while in refluxing toluene bridge isomers Fe₂(CO)₄{μ-Ph₂PN(R)PPh₂}(μ-pdt) are the major products. Separate studies have shown that chelate complexes convert to the bridge isomers at higher temperatures. Two pairs of bridge and chelate isomers (R = allyl, ⁱPr) have been crystallographically characterised together with Fe₂(CO)₄{μ-Ph₂PN(H)PPh₂}(μ-pdt). Chelate complexes adopt the dibasal diphosphine arrangement in the solid state and exhibit very small P–Fe–P bite-angles, while the bridge complexes adopt the expected cisoid dibasal geometry. Density functional calculations have been carried out on the chelate and bridge isomers of the model compound Fe₂(CO)₄{Ph₂PN(Me)PPh₂}(μ-pdt) and reveal that the bridge isomer is thermodynamically favourable relative to the chelate isomers that are isoenergetic. The HOMO in each of the three isomers exhibits significant metal–metal bonding character, supporting a site-specific protonation of the iron–iron bond upon treatment with acid. Addition of HBF₄·Et₂O to the Fe₂(CO)₄{κ²-Ph₂PN(allyl)PPh₂}(μ-pdt) results in the clean formation of the corresponding dibasal hydride complex [Fe₂(CO)₄{κ²-Ph₂PN(allyl)PPh₂}(μ-H)(μ-pdt)][BF₄], with spectroscopic measurements revealing the intermediate formation of a basal–apical isomer. A crystallographic study reveals that there are only very small metric changes upon protonation. In contrast, the bridge isomers react more slowly to form unstable species that cannot be isolated. Electrochemical and electrocatalysis studies have been carried out on the isomers of Fe₂(CO)₄{Ph₂PN(allyl)PPh₂}(μ-pdt). Electron accession is predicted to occur at an orbital that is anti-bonding with respect to the two metal centres based on the DFT calculations. The LUMO in the isomeric model compounds is similar in nature and is best described as an antibonding Fe–Fe interaction that contains differing amounts of aryl π* contributions from the ancillary PNP ligand. The proton reduction catalysis observed under electrochemical conditions at ca. −1.55 V is discussed as a function of the initial isomer and a mechanism that involves an initial protonation step involving the iron–iron bond. The measured CV currents were higher at this potential for the chelating complex, indicating faster turnover. Digital simulations showed that the faster rate of catalysis of the chelating complex can be traced to its greater propensity for protonation. This supports the theory that asymmetric distribution of electron density along the iron–iron bond leads to faster catalysis for models of the Fe–Fe hydrogenase active site.

The diiron complex Fe ₂ (CO) ₄ (μ-dppf)(μ-pdt) is an active catalyst for both the reduction of protons to give hydrogen and also the reverse oxidation of hydrogen and thus mimics hydrogenases which are able to catalyse both reactions.