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The intermolecular complexes formed between imidazol-2-ylidene and its heavy-atom analogues C2H4N2X: (X = C, Si, Ge, Sn, Pb) and YH3F (Y = Si, Ge, Sn, Pb) have been optimized at the MP2/aug-cc-pVTZ level. C2H4N2X: have two electron-rich moieties, one of which is the lone pair on the X atom and the other is the 6π-electron system. Three types of binding modes (type-A, type-B and type-C) can be distinguished for C2H4N2X: according to the locations of YH3F. The type-A and type-B complexes can be located for C2H4N2C:···YH3F system, and the Eint values of the type-A complexes are much larger than those of the type-B complexes. The type-A, type-B and type-C complexes can be located for the other four systems, and the Eint values of these complexes go in the order type-B > type-C > type-A. The binding strength of the type-A complexes becomes weaker, and that of the type-B and type-C complexes becomes stronger with the increase of the X atomic number for C2H4N2X:···YH3F system, which can be clarified by the MEP maps of C2H4N2X:. The NBO, AIM and SAPT analysis was employed to explore the nature of the interactions in these complexes. [ABSTRACT FROM AUTHOR]

The dual binding behavior of the metallylenes TH2 (T = Si, Ge, Sn, Pb) with some selected Lewis acids (T'H3F, T' = Si, Ge, Sn, Pb) and bases (N2, HCN, CO, and C6H6) has been investigated by using the high-level quantum chemical method. Two types (type-A and type-B) of tetrel-bonded complexes can be formed for TH2 due to their ambiphilic character. TH2 act as Lewis bases in type-A complexes, and they act as Lewis acids in type-B ones. CO exhibits two binding modes in the type-B complexes, one of which is TH2···CO and the other is TH2···OC. The TH2···OC complexes possess a weaker binding strength than the other type-B complexes. The TH2···OC complexes are referred to as the type-B2 complexes, and the other type-B complexes are referred to as the type-B1 complexes. The type-A complexes exhibit a relatively weak binding strength with Eint (interaction energy) values ranging from –7.11 to –15.55 kJ/mol, and the type-B complexes have a broad range of Eint values ranging from −9.45 to −98.44 kJ/mol. The Eint values of the type-A and type-B1 complexes go in the order SiH2 > GeH2 > SnH2 > PbH2. The AIM (atoms in molecules) analysis suggests that the tetrel bonds in type-A complexes are purely closed-shell interactions, and those in most type-B1 complexes have a partially covalent character. The EDA (Energy decomposition analysis) results indicate that the contribution values of the three energy terms go in the order electrostatic > dispersion > induction for the type-A and type-B2 complexes, and this order is electrostatic > induction > dispersion for the type-B1 complexes. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • The chalcogen-bonded and tetrel-bonded complexes between the singlet metallylenes and carbonyl chalcogenides are investigated and compared. • The dual binding behavior of the metallylenes and carbonyl chalcogenides can be explained on the basis of the molecular electrostatic potential surfaces. • The nature of the complexes has been investigated by the NBO, AIM and SAPT analysis. The intermolecular interactions between the singlet metallylenes XH 2 (X = Si, Ge, Sn, Pb) and carbonyl chalcogenides OCY (Y = S, Se, Te) have been studied by the high-level quantum chemical calculations. The chalcogen-bonded and tetrel-bonded complexes can be formed between XH 2 and OCY due to their ambiphilic character. The structure and binding strength of the complexes have been explored on the basis of the MEP surfaces of the monomers, and geometrical parameters and interaction energies of the complexes. The nature of the complexes has been investigated by the NBO, AIM and SAPT analysis. The tetrel-bonded complexes exhibit a much stronger binding strength with larger interaction energies and shorter binding distances compared to the chalcogen-bonded complexes. The interaction energies of the complexes become larger with the increase of the Y atomic number, but become smaller with the increase of the X atomic number. NBO analysis reveals that the dominant orbital interactions in the chalcogen-bonded and tetrel-bonded complexes are LP(X) → σ*(C-Y) and LP(Y) → LP*(X), respectively. AIM analysis suggests that the chalcogen-bonded complexes are the purely noncovalent, but the tetrel-bonded complexes have partial covalent character. SAPT analysis indicates that the contribution of the energy component decreases in the order of E ele > E disp > E ind for most chalcogen-bonded complexes, and this order is E ele > E ind > E disp for most tetrel-bonded complexes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The various hydrogen-bonded complexes involving the imidazol-2‑ylidene and its heavier congeners are investigated and compared. • Two types of hydrogen-bonded geometries can be located on the basis of the molecular electrostatic potential surfaces. • The relaxed potential energy surface scans were performed for some selected complexes. The hydrogen-bonded complexes formed between the imidazol-2‑ylidene and its heavier congeners C 2 H 4 N 2 T: (T = C, Si, Ge, Sn, Pb) and the three selected electron acceptors (HF, HCN and C 2 H 2) have been optimized at the aug-cc-pVTZ level, and the nature of these complexes has been investigated by natural bond orbital (NBO), atoms in molecules (AIM) and energy decomposition analyses. The complexes can be classified into type-A structure and type-B structure according to the location of the electron acceptors. The electron acceptors are around T atoms of C 2 H 4 N 2 T: for the type-A complexes, and the electron acceptors are above the five-membered ring (π-system) of C 2 H 4 N 2 T: for the type-B complexes. The electron-donating ability of T atoms becomes weaker, and that of π-systems becomes stronger when T atoms become heavier for C 2 H 4 N 2 T:, which is consistent with the molecular electrostatic potentials (MEP) maps of C 2 H 4 N 2 T:. For a given C 2 H 4 N 2 T:, the E int values of the type-A complexes go in the order HF > HCN > C 2 H 2 , and the E int values of the type-B complexes go in the order HF ≈ HCN > C 2 H 2. The contribution of electrostatic energy to the interaction energy of complexes becomes smaller for the type-A complexes when the T atoms become heavier. The interaction energies are dominated by the electrostatic energies for all the type-B complexes involving HF, and the interaction energies are dominated by the dispersion energies for most type-B complexes involving HCN and C 2 H 2. The relaxed potential energy surface scans were performed for some selected complexes involving HF and HCN to examine the difference in binding behavior between HF and HCN. [ABSTRACT FROM AUTHOR]