Qingzhong Li

Pnicogen-hydride interaction between FH2X (X = P and As) and HM (M = ZnH, BeH, MgH, Li, and Na).

A pnicogen-hydride interaction has been predicted and characterized in FH(2)P-HM and FH(2)As-HM (M = ZnH, BeH, MgH, Li, and Na) complexes at the MP2/aug-cc-pVTZ level. For the complexes analyzed here, P(As) and HM are treated as a Lewis acid and a Lewis base, respectively. This interaction is moderate or strong since, for the strongest interaction of the FH(2)As-HNa complex, the interaction energy amounts to -24.79 kcal/mol, and the binding distance is equal to about 1.7 Å, much less than the sum of the corresponding van der Waals radii. By comparison with some related systems, it is concluded that the pnicogen-hydride interactions are stronger than dihydrogen bonds and lithium-hydride interactions. This interaction has been analyzed with natural bond orbitals, atoms in molecules, electron localization function, and symmetry adapted perturbation theory methods.

Tetrel-hydride interaction between XH₃F (X = C, Si, Ge, Sn) and HM (M = Li, Na, BeH, MgH).

A tetrel-hydride interaction was predicted and characterized in the complexes of XH3F···HM (X = C, Si, Ge, Sn; M = Li, Na, BeH, MgH) at the MP2/aug-cc-pVTZ level, where XH3F and HM are treated as the Lewis acid and base, respectively. This new interaction was analyzed in terms of geometrical parameters, interaction energies, and spectroscopic characteristics of the complexes. The strength of the interaction is essentially related to the nature of X and M groups, with both the larger atomic number of X and the increased reactivity of M giving rise to a stronger tetrel-hydride interaction. The tetrel-hydride interaction exhibits similar substituent effects to that of dihydrogen bonds, where the electron-donating CH3 and Li groups in the metal hydride strengthen the binding interactions. NBO analyses demonstrate that both BD(H-M) → BD*(X-F) and BD(H-M) → BD*(X-H) orbital interactions play the stabilizing role in the formation of the complex XH3F···HM (X = C, Si, Ge, and Sn; M = Li, Na, BeH, and MgH). The major contribution to the total interaction energy is electrostatic energy for all of the complexes, even though the dispersion/polarization parts are nonnegligible for the weak/strong tetrel-hydride interaction, respectively.

Influence of Substitution, Hybridization, and Solvent on the Properties of C−HO Single-Electron Hydrogen Bond in CH3−H2O Complex

The effect of substitution, hybridization, and solvent on the properties of the C...HO single-electron hydrogen bond has been investigated with quantum chemical calculations. Methyl radical, ethyl radical, and vinyl radical are used as the proton acceptors and are paired with water, methanol, HOCl, and vinyl alcohol. Halogenation (Cl) of the proton donor strengthens this type of hydrogen bond. The methyl group in the proton donor and proton acceptor plays a different role in the formation of the C...HO single-electron hydrogen bond. The former is electron-withdrawing, and the latter is electron-donating, both making a constructive contribution to the enhancement of the interaction. The contribution of the methyl group in the proton acceptor is larger than that in the proton donor. The increase of acidity of the proton is helpful to form a single-electron hydrogen bond. As the proton acceptor varies from the methyl radical to the vinyl radical, the interaction strength also increases. The solvent has an enhancing influence on the strength of the C...HO single-electron hydrogen bond. These factors affect the C...HO single-electron hydrogen bond in a similar way that they do other types of hydrogen bonds.

Regulating function of methyl group in strength of CH...O hydrogen bond: a high-level ab initio study.

An ab initio computational study of the regulating function of the methyl group in the strength of the CH...O hydrogen bond (HB) with XCC-H (X = H, CH3, F) as a HB donor and HOY (Y = H, CH3, Cl) as a HB acceptor has been carried out at the MP2/aug-cc-pVDZ and MP2/aug-cc-pVTZ levels. The bond lengths, interaction energies, and stretching frequencies are compared in the gas phase. The results indicate that the methyl substitution of the proton acceptor strengthens the CH...O HB, whereas that of the proton donor weakens the CH...O HB. NBO analysis demonstrates that the methyl group of the proton acceptor is electron-withdrawing and that of the proton donor is electron-donating in the formation of the CH...O HB. The electron-donation of the methyl group in the proton acceptor plays a positive contribution to the formation of the CH...O HB, whereas the electron-withdrawing action of the methyl group in the proton donor plays a negative contribution to the formation of the CH...O HB. The positive contribution of methyl group in the proton acceptor is larger than the negative contribution of methyl group in the proton donor.

Ab Initio Study of Lithium-Bonded Complexes with Carbene as an Electron Donor

The complexes H(2)C-LiX (X = H, OH, F, Cl, Br, CN, NC, CH(3), C(2)H(3), C(2)H, NH(2)) have been studied with quantum chemical calculations at the MP2/6-311++G(d,p) level. A new type of lithium bond was proposed, in which the carbene acts as the electron donor. This new type of lithium bond was characterized in view of the geometrical, spectral and energetic parameters. The Li-X bond elongates in all lithium bonded complexes. The Li-X stretch vibration has a red shift in the complexes H(2)C-LiX (X = H, OH, F); however, it exhibits a blue shift in the complexes H(2)C-LiX (X = Cl, Br, CN, NC, CH(3), C(2)H(3), C(2)H, NH(2)). The binding energies are in a range of 16.88-21.13 kcal/mol, indicating that the carbene is a good electron donor in the interaction. The energy decomposition analyses show that the electrostatic contribution is largest, polarization counterpart is followed, and charge transfer is smallest. The effect of substitution and hybridization on this type of lithium bond has also been investigated.

Prominent Effect of Alkali Metals in Halogen-Bonded Complex of MCCBr−NCM′ (M and M′ = H, Li, Na, F, NH2, and CH3)

Quantum chemical calculations have been performed for the MCCBr−NCM′ (M and M′ = H, Li, Na, F, NH2, and CH3) halogen-bonded complexes at the MP2/aug-cc-pVTZ level. The binding energy is in a range of 1.34−23.42 kJ/mol. The results show that the alkali metal has a prominent effect on the strength of halogen bond, and this effect is different for the alkali metal in the halogen and electron donors. The alkali atom in the halogen donor makes it weaken greatly, whereas that in the electron donor causes it to enhance greatly. Natural bond orbital analysis shows that the alkali atom is electron-withdrawing in the halogen donor and electron-donating in the electron donor. In formation of the halogen bond, the former is a negative contribution, whereas the latter is a positive one. A similar charge transfer is also found for the H atom in the halogen and electron donors. These complexes have also been analyzed with the atoms in molecules theory.

Novel Halogen-Bonded Complexes H3NBH3···XY (XY = ClF, ClCl, BrF, BrCl, and BrBr): Partially Covalent Character

Quantum chemical calculations have been performed to study the interaction of H(3)NBH(3) with dihalogen molecules XY (XY = ClF, ClCl, BrF, BrCl, and BrBr) at the MP2/aug-cc-pVTZ level. It is shown that a halogen-hydride halogen bond is formed between the two molecules, in which the sigma electron of the B-H bond in H(3)NBH(3) acts as the electron donor. The strength of the halogen bond ranges from 14.82 kJ/mol in H(3)NBH(3)-ClCl complex to 40.13 kJ/mol in H(3)NBH(3)-BrF complex at the CCSD(T)/aug-cc-pVTZ level, which is comparable to medium strong hydrogen bonds. The B-H and X-Y bonds are elongated with a concomitance of a red shift. The analyses of natural bond orbital and atoms in molecules have been carried out to understand the nature of properties of this novel interaction. The results show that this interaction has partially covalent character.

Influence of hybridization and cooperativity on the properties of Au-bonding interaction: comparison with hydrogen bonds.

Quantum chemical calculations have been performed to study the hybridization effect in H(2)O-AuCH(2)CH(3), H(2)O-AuCHCH(2), and H(2)O-AuCCH dimers, and the cooperativity between the hydrogen bond and Au bonding in three trimers (T1, T2, and T3) composed of one AuCCH and two H(2)O molecules. With regard to the organic Au compounds, sp-hybridized AuCCH forms the strongest Au bonding, followed by sp(2) and then sp(3). The C-Au bond is elongated, and its elongation becomes larger with the increase of the s character in hybrid orbitals, whereas the corresponding stretch vibration displays a small blue shift. The positive cooperativity is present for the hydrogen bond and Au bonding in T1 and T2 trimers, whereas the negative cooperativity is found in T3 trimer. The results show that the hybridization effect and cooperative interaction in Au bonding are similar to those in hydrogen bonds. Additionally, an OH···Au hydrogen bond is suggested in T1 trimer.

Gigantic Blue Shift of the H-Ar Stretch Vibration in π Hydrogen-Bonded C2H2 ··· HArCCF Complex

Quantum chemical calculations have been performed to study the structure and properties of the pi hydrogen-bonded complex formed between acetylene and HArCCF at the MP2/6-311++G(2d,2p) level. The C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes were also studied for comparison with the C(2)H(2)...HArCCF complex. The basis set superposition errors (BSSE)-counterpoise corrected potential-energy surface (PES) has a larger influence on the structure and properties of the C(2)H(2)...HArCCF complex than those of the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes. The C(2)H(2)...HArCCF complex exhibits a very large harmonic vibrational frequency blue shift of 574 cm(-1) for the H-Ar stretch, whereas the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes exhibit a small red shift of 35 and 47 cm(-1) for the H-C stretch, respectively; upon complexation the IR intensity decreases in the former, whereas it increases in the latter. The origin of the frequency shift and nature of the hydrogen bond in these complexes have been unveiled with the natural bond orbital analysis and energy decomposition.