Theoretical studies on the dimers formed by CO with the halides of multivalent astatine as a Lewis-acid center are carried out to examine the typical characteristics of supervalent halogen bonds.

Intermolecular interaction of XH2P···MY (X = H, CH3, F, CN, NO2; M = Cu, Ag, Au; Y = F, Cl, Br, I) complexes was investigated by means of an ab initio method. The molecular interaction energies are in the order Ag < Cu < Au and increased with the decrease of RP···M. Interaction energies are strengthened when electron-donating substituents X connected to XH2P, while electron-withdrawing substituents produce the opposite effect. The strongest P···M bond was found in CH3H2P···AuF with −70.95 kcal/mol, while the weakest one was found in NO2H2P···AgI with −20.45 kcal/mol. The three-center/four-electron (3c/4e) resonance-type of P:-M-:Y hyperbond was recognized by the natural resonance theory and the natural bond orbital analysis. The competition of P:M–Y ↔ P–M:Y resonance structures mainly arises from hyperconjugation interactions; the bond order of bP–M and bM–Y is in line with the conservation of the idealized relationship bP–M + bM–Y ≈ 1. In all MF-containing complexes, P–M:F resonance accounted for a larger proportion which leads to the covalent characters for partial ionicity of MF. The interaction energies of these Cu/Ag/Au complexes are basically above the characteristic values of the halogen-bond complexes and close to the observed strong hydrogen bonds in ionic hydrogen-bonded species.

No abstract

Zirconium-based metal–organic frameworks (Zr-MOFs) with Zr6 inner cores represent a subfamily of nanoporous materials with good physicochemical stabilities, showing significant prospect for practical applications in various fields. Although computational characterization can play an important role that is complementary to experimental efforts, the availability of chemically realistic Zr-MOF structures is one of the prerequisites to accurately evaluate their performance as well as provide valuable insights for guiding material design. In this work, periodic density functional theory (DFT) calculations combined with a molecular mechanics method were performed to optimize the crystalline structures of over 182 experimentally synthesized Zr-MOFs that contain no less than 10-coordinated Zr6O8 nodes, leading to a database consisting of the structures having a diversity of topologies, pore sizes, and functionalities. Apart from determination of favorable configurations of organic linkers, rational proton topologies of the 11- and 10-coordinated Zr6O8 nodes were also clarified. Computational screening was further conducted to examine the H2S/CH4 separation properties of each material in the database. Significant difference were observed by comparing the separation properties of Zr-MOFs with optimized and nonoptimized structures. Some promising candidates with high H2S adsorption capacity and separation selectivity were identified on the basis of some evaluation metrics, and favorable organic linkers for designing new high-performance Zr-MOFs were also proposed.