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Hypohalous acids (HOX) are a class of molecules that play a key role in the atmospheric seasonal depletion of ozone and have the ability to form both hydrogen and halogen bonds. The interactions between the HOX monomers (X = F, Cl, Br) and water have been studied at the CCSD(T)/aug-cc-pVTZ level of theory with the spin free X2C-1e method to account for scalar relativistic effects. Focal point analysis was used to determine CCSDT(Q)/CBS dissociation energies. The anti hydrogen bonded dimers were found with interaction energies of −5.62 kcal mol −1 , −5.56 kcal mol −1 , and −4.97 kcal mol −1 for X = F, Cl, and Br, respectively. The weaker halogen bonded dimers were found to have interaction energies of −1.71 kcal mol −1 and −3.03 kcal mol −1 for X = Cl and Br, respectively. Natural bond orbital analysis and symmetry adapted perturbation theory were used to discern the nature of the halogen and hydrogen bonds and trends due to halogen substitution. The halogen bonds were determined to be weaker than the analogous hydrogen bonds in all cases but close enough in energy to be relevant, significantly more so with increasing halogen size. 

Pnictinidenes are an increasingly relevant species in main group chemistry and generally exhibit proclivity for the triplet electronic ground state. However, the elusive singlet electronic states are often desired for chemical applications. We predict the singlet‐triplet energy differences (ΔE_ST=E_Singlet−E_Triplet) of simple group 15 and 16 substituted pnictinidenes (Pn−R; Pn=P, As, Sb, or Bi) with highly reliable focal‐point analyses targeting the CCSDTQ/CBS level of theory. The only cases we predict to have favorable singlet states are P−PH₂(−3.2 kcal mol⁻¹) and P−NH₂(−0.2 kcal mol⁻¹). ΔE_STtrends are discussed in light of the geometric predictions as well as qualitative natural bond order analysis to elucidate some of the important electronic structure features. Our work provides a rigorous benchmark for the ΔE_STof fundamental Pn−R moieties and provides a firm foundation for the continued study of heavier pnictinidenes.

 

Despite the interest in sulfur monoxide (SO) among astrochemists, spectroscopists, inorganic chemists, and organic chemists, its interaction with water remains largely unexplored. We report the first high level theoretical geometries for the two minimum energy complexes formed by sulfur monoxide and water, and we report energies using basis sets as large as aug-cc-pV(Q+d)Z and correlation effects through perturbative quadruple excitations. One structure of SO⋯H 2 O is hydrogen bonded and the other chalcogen bonded. The hydrogen bonded complex has an electronic energy of −2.71 kcal mol −1 and a zero kelvin enthalpy of −1.67 kcal mol −1 , while the chalcogen bonded complex has an electronic energy of −2.64 kcal mol −1 and a zero kelvin enthalpy of −2.00 kcal mol −1 . We also report the transition state between the two structures, which lies below the SO⋯H 2 O dissociation limit, with an electronic energy of −1.26 kcal mol −1 and an enthalpy of −0.81 kcal mol −1 . These features are much sharper than for the isovalent complex of O 2 and H 2 O, which only possesses one weakly bound minimum, so we further analyze the structures with open-shell SAPT0. We find that the interactions between O 2 and H 2 O are uniformly weak, but the SO⋯H 2 O complex surface is governed by the superior polarity and polarizability of SO, as well as the diffuse electron density provided by sulfur's extra valence shell.