Faraday Discussions最新文献

Copper clusters on carbide surfaces have shown a high catalytic activity towards methanol formation. To understand the interaction between CO₂ and the catalytically active sites during this process and the role that carbon atoms could play in this, they are modeled by copper clusters, with carbon atoms incorporated. The formed clusters Cu_nC_m^? (n = 3–10, m = 1–2) are reacted with CO₂ and investigated by IR multiple-photon dissociation (IR-MPD) spectroscopy to probe the degree of CO₂ activation. IR spectra for the reaction products [Cu_nC·CO₂]^?, (n = 6–10), and [Cu_nC₂·CO₂]^?, (n = 3–8) are compared to reference spectra recorded for products formed when reacting the same cluster sizes with CO, and with density functional theory (DFT) calculated spectra. The results reveal a size- and carbon load-dependent activation and dissociation of CO₂. The complexes [Cu_nC·CO₂]^? with n = 6 and 10 show predominantly molecular activation of CO₂, while those with n = 7–9 show only dissociative adsorption. The addition of the second carbon to the cluster leads to the exclusive molecular activation of the CO₂ on all measured cluster sizes, except for Cu₅C₂^? where CO₂ dissociates. Combining these findings with DFT calculations leads us to speculate that at lower carbon-to-metal ratios (CMRs), the C can act as an oxygen anchor facilitating the OCO bond rupture, whereas at higher CMRs the carbon atoms increasingly attract negative charge, reducing the Cu cluster’s ability to donate electron density to CO₂, and consequently its ability to activate CO₂.

During the past 10 years, biological electron cryo-microscopy (cryoEM) has undergone a process of rapid transformation. Many things we could only dream about a decade ago have now become almost routine. Nevertheless, a number of challenges remain, to do with sample preparation, the correlation between tomographic analysis and light microscopy, data validation, and the growing impact of artificial intelligence and structure prediction. This year’s Faraday Discussion examined these challenges in some detail. The concluding remarks present a concise summary of the meeting and a brief outlook to the future.

MSn₁₂ clusters (M = Al, Ga, In) were studied in electric and magnetic beam deflection experiments at temperatures of 16 K and 30 K. For all three species, the results of the electric beam deflection experiments indicate the presence of two structural isomers of which one is considerably polar. The magnetic beam deflection experiments show atom-like beam splitting (superatomic behavior) with g-factors of 2.6–2.7 for a fraction of the clusters in the molecular beam, indicating significant spin–orbit coupling. On the one hand, we investigate by several experiments combining electric and magnetic deflectors how the superatomic and polar fractions are linked proving the correlation of the Stark and Zeeman effects. On the other hand, the magnetic deflection behavior is examined more thoroughly by performing quantum chemical calculations. By systematic distortion of an artificial icosahedral tin cage towards the global minimum structure, which has a pyritohedral geometry, the shifts in the magnitude of the g-factor are found to be mainly caused by a single dominant electronic excitation. This allows one to develop a semi-quantitative understanding of the magnetic behavior. On the basis of avoided crossings in the rotational Zeeman diagram, simulations of the magnetic beam deflection comprising computed rotational constants, vibrational modes, g-factors and spin–rotation coupling constants are performed which resemble our experimental findings in satisfactory agreement. With this, a better understanding of the magnetic properties of nanoalloy clusters can be achieved. However, the geometric structures of the polar isomers are still unknown.