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Methods: The intermolecular interactions between the heavy-atom analogues of acetylene T2H2 (T = Si, Ge, Sn, Pb) and HCN have been investigated by theoretical calculations at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level. Results: The global energy minimum of T2H2 is the butterfly structure A, and another energy minimum is the planar structure B. Both structures A and B exhibit the dual behavior when binding with HCN. The various hydrogen bond (HB), dihydrogen bond (DB) and tetrel bond (TB) complexes can be found according to the MEP maps of T2H2. One TB and three HB complexes formed between structure A and HCN can be located for Si2H2 and Ge2H2. One TB, two HB and one DB complexes formed between structure A and HCN can be located for Sn2H2 and Pb2H2. Four TB and one HB complexes formed between structure B and HCN can be located for all the T2H2. The geometries and binding strengths of the complexes are compared and analyzed. Conclusions: The interactions in these complexes are generally weak, and the interaction energies of these complexes range from −0.53 to −8.23 kcal/mol. The interaction energies of the TB complexes are larger than those of the corresponding HB and DB complexes for structure A···HCN systems. The relative binding strength of the four TB complexes exhibits different order for different structure B···HCN systems, which is consistent with the MEP maps of the isolated monomers. [ABSTRACT FROM AUTHOR]

The binding behavior of coinage metal anions with some electron-deficient arenes has been investigated by MP2 calculations, and the character of interactions in these complexes has been examined by NBO analysis. The results indicate that coinage metal anions can interact with electron-deficient arenes to form anion-π, strong σ-type and hydrogen-bonding complexes. The σ-type structure is the global minimum for triazine, trifluorotriazine, hexafluorobenzene and tricyanobenzene, and the hydrogen-bonding structure is the global minimum for trifluorobenzene. There exist some differences in the stability of anion-π complexes for coinage metal anions: the anion-π complexes of Au are minima expect for triazine complex; the anion-π complexes of Ag are minima expect for tricyanobenzene complex; and the anion-π complexes of Cu are not minima expect for trifluorobenzene complex. The binding strength of anion-π and hydrogen-bonding complexes for Au is larger than that for Ag and Cu, but the binding strength of σ complex displays a different sequence: Cu > Au > Ag. The binding behavior of coinage metal anions is more similar to that of F than that of Cl and Br. The relaxed potential energy surface scans for some selected systems have been performed to help understand the interactions between coinage metal anions with electron-deficient arenes. [ABSTRACT FROM AUTHOR]

Highlights: [•] The anion-binding ability of FH2As is stronger than that of FH2P. [•] The binding strength is in the sequence of SO4 2− >F− >Cl− >NO3 − >Br− >I−. [•] The anion-binding strength of pnicogen bonding is comparable to that of hydrogen and halogen bonding. [•] The anion-binding ability of pnicogen bonding can be strengthened through multiple receptor–anion interactions. [Copyright &y& Elsevier]

The ternary complexes X · 1 · YF ( 1 = triazine, X = Cl, Br and I, Y = H, Cl, Br, I, PH and AsH) have been investigated by MP2 calculations to understand the noncovalently electron-withdrawing effects on anion-arene interactions. The results indicate that in binary complexes ( 1 · X), both weak σ-type and anion-π complexes can be formed for Cl and Br, but only anion-π complex can be formed for I. Moreover, the hydrogen-bonding complex is the global minimum for all three halides in binary complexes. However, in ternary complexes, anion-π complex become unstable and only σ complex can retain in many cases for Cl and Br. Anion-π complex keeps stable only when YF = HF. In contrast with binary complexes, σ complex become the global minimum for Cl and Br in ternary complexes. These changes in binding mode and strength are consistent with the results of covalently electron-withdrawing effects. However, in contrast with the covalently electron-withdrawing substituents, Cl and Br can attack the aromatic carbon atom to form a strong σ complex when the noncovalently electron-withdrawing effect is induced by halogen bonding. The binding behavior for I is different from that for Cl and Br in two aspects. First, the anion-π complex for I can also keep stable when the noncovalent interaction is halogen bonding. Second, the anion-π complex for I is the global minimum when it can retain as a stable structure. [ABSTRACT FROM AUTHOR]