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The structure, stability, and bonding character of fifteen (Ng-H-Ng)+ and (Ng-H-Ng’)+ (Ng, Ng’ = He-Xe) compounds were explored by theoretical calculations performed at the coupled cluster level of theory. The nature of the stabilizing interactions was, in particular, assayed using a method recently proposed by the authors to classify the chemical bonds involving the noble-gas atoms. The bond distances and dissociation energies of the investigated ions fall in rather large intervals, and follow regular periodic trends, clearly referable to the difference between the proton affinity (PA) of the various Ng and Ng’. These variations are nicely correlated with the bonding situation of the (Ng-H-Ng)+ and (Ng-H-Ng’)+. The Ng-H and Ng’-H contacts range, in fact, between strong covalent bonds to weak, non-covalent interactions, and their regular variability clearly illustrates the peculiar capability of the noble gases to undergo interactions covering the entire spectrum of the chemical bond.

The structure, stability, and bonding situation of some exemplary noble gas-silicon cations were investigated at the MP2/aVTZ level of theory. The explored species include the mono-coordinated NgSiX3+ (Ng = He-Rn; X = H, F, Cl) and NgSiF22+ (Ng = He-Rn), the di-coordinated Ar2SiX3+ (X = H, F, Cl), and the “inserted” FNgSiF2+ (Ng = Kr, Xe, Rn). The bonding analysis was accomplished by the method that we recently proposed to assay the bonding situation of noblegas compounds. The Ng-Si bonds are generally tight and feature a partial contribution of covalency. In the NgSiX3+, the degree of the Ng-Si interaction mirrors the trends of two factors, namely the polarizability of Ng that increases when going from Ng = He to Ng = Rn, and the Lewis acidity of SiX3+ that decreases in the order SiF3+ > SiH3+ > SiCl3+. For the HeSiX3+, it was also possible to catch peculiar effects referable to the small size of He. When going from the NgSiF3+ to the NgSiF22+, the increased charge on Si promotes an appreciable increase inthe Ng-Si interaction, which becomes truly covalent for the heaviest Ng. The strength of the bond also increases when going from the NgSiF3+ to the “inserted” FNgSiF2+, likely due to the cooperative effect of the adjacent F atom. On the other hand, the ligation of a second Ar atom to ArSiX3+ (X = H, F, Cl), as to form Ar2(SiX3+), produces a weakening of the bond. Our obtained data were compared with previous findings already available in the literature.

The design of complex molecular machines and devices represents one of the most ambitious frontiers in nanotechnology, synthetic chemistry, and molecular engineering. These intricate systems, inspired by biological machines, require precise control over atomic and electronic interactions to achieve desired functionalities. Theoretical modeling plays a crucial role in this process, offering predictive insights into molecular behavior, guiding experimental design, and optimizing performance. Methods such as density functional theory, quantum theory of atoms in molecules coupled with widely adopted and distinctive visualization methods, molecular dynamics simulations, and quantum mechanical/molecular mechanical hybrid approaches provide analytical information into the stability in terms of mutual chemical interactions and conformational shaping of flexible supramolecular aggregates for nanotechnological applications. Theoretical approaches also facilitate interdisciplinary integration, bridging chemistry, physics, and materials science to create conceptually hybrid devices with enhanced performance. Machine learning and artificial intelligence are now being incorporated into theoretical modeling, accelerating the discovery and refinement of novel molecular architectures. This fusion of data‐driven approaches with traditional computational chemistry algorithms is expected to revolutionize the design paradigm of soft molecular machines and devices. Theoretical approaches facilitate interdisciplinary integration, bridging chemistry, physics, and materials science to create conceptually hybrid devices with enhanced performance. Machine learning and artificial intelligence are now being incorporated into theoretical modeling, accelerating the discovery of novel molecular architectures. This fusion is expected to revolutionize the design paradigm of soft molecular machines and devices.

The structure, stability, and bonding character of some exemplary LAr and L-ArBeO (L = He, Ne, Ar, N2, CO, F2, Cl2, ClF, HF, HCl, NH3) were investigated by MP2 and coupled-cluster calculations, and by symmetry-adapted perturbation theory. The nature of the stabilizing interactions was also assayed by the method recently proposed by the authors to classify the chemical bonds in noble-gas compounds. The comparative analysis of the LAr and L-ArBeO unraveled geometric and bonding effects peculiarly related to the σ-hole at the Ar atom of ArBeO, including the major stabilizing/destabilizing role of the electrostatic interactionensuing from the negative/positive molecular electrostatic potential of L at the contact zone with ArBeO. The role of the inductive and dispersive components was also assayed, making it possible to discern the factors governing the transition from the (mainly) dispersive domain of the LAr, to the σ-hole domain of the L-ArBeO. Our conclusions could be valid for various types of non-covalent interactions, especially those involving σ-holes of respectable strength such as those occurring in ArBeO.

The landmark synthesis of a xenon compound in the early 1960s dispelled a long-standing myth about the reactivity of the noble gases — and opened the door to the rich chemistry of these elements, studies of which continue today. How the synthesis of a xenon compound founded a field of research.

Felice Grandinetti ponders on the peculiarity of neon among the noble gases — and whether it should occupy the top-right position in the periodic table.

The structure, stability, and bonding character of fifteen (Ng-H-Ng) and (Ng-H-Ng') (Ng, Ng' = He-Xe) compounds were explored by theoretical calculations performed at the coupled cluster level of theory. The nature of the stabilizing interactions was, in particular, assayed using a method recently proposed by the authors to classify the chemical bonds involving the noble-gas atoms. The bond distances and dissociation energies of the investigated ions fall in rather large intervals, and follow regular periodic trends, clearly referable to the difference between the proton affinity (PA) of the various Ng and Ng'. These variations are nicely correlated with the bonding situation of the (Ng-H-Ng) and (Ng-H-Ng') . The Ng-H and Ng'-H contacts range, in fact, between strong covalent bonds to weak, non-covalent interactions, and their regular variability clearly illustrates the peculiar capability of the noble gases to undergo interactions covering the entire spectrum of the chemical bond.