N2O…HOCl复合物结构和性质的理论研究

分别在DFT-B3LYP和MP2/6-311++G**水平上求得HOCl + N2O复合物势能面上的六种(S1, S2, S3, S4, S5和S6)和四种(S1, S2, S4和S5)构型. 频率分析表明,其中的S1和S3为过渡态,其它为稳定构型. 在复合物S3, S5 和S6中,HOCl 单体的σ*(5O-6H)作为质子供体,与N2O单体中作为质子受体的3O原子相互作用,形成氢键结构,而在氢键复合物S2中, 质子受体为N2O单体中的端1N原子;复合物S1中,HOCl分子的σ*(5O-4Cl)作为质子供体与N2O分子中的端1N原子(质子受体)相互作用,形成卤键结构,而复合物S4中的卤键结构的质子受体为N2O分子中的端3O原子. 经B3LYP/6-311++G**水平上的计算,考虑了基组重叠误差(BSSE)校正的单体间相互作用能在-1.56 ~ -8.73 kJ·mol-1之间. 采用自然键轨道理论(NBO)对两种单体间相互作用的本质进行了考查,并通过分子中原子理论(AIM)分析了复合物中氢键和卤键键鞍点处的电子密度拓扑性质.     

Theoretical study of hydrogen bonded complexes of dimethyl disulfide or dimethyl peroxide with nitric acid

Ab initio and DFT calculations performed on the title systems revealed two types of structures for both DMDS-HNO₃ and DMDO-HNO₃ complexes. In both structures two hydrogen bonds are formed between the OH group interacting with one of sulfur (or oxygen) atoms and methyl CH group being a proton donor to one of the oxygen atoms of the NO₂ group of nitric acid. Depending on the location of the interacting methyl group with respect to the S or O acceptor of the main O-H?S(O) bond, the seven or eight-membered ring structures are formed. For all the structures, the most pronounced changes in geometric parameters upon interaction are observed for the proton donor molecule. The calculated binding energies are between −20.86 and −29.95 kJ/mol at MP2 and between −17.52 and −27.47 kJ/mol at B3LYP using the 6-311++G(2d,2p) basis set. The complexes involving disulfide are slightly weaker by ca. 6.7-8.6 kJ/mol than the corresponding peroxide complexes. The performed NBO analysis reveals that the charge transferred to σ*(OH) orbital of the nitric acid molecule comes mainly from the high p-character lone pair orbital of sulfur or oxygen atom being the hydrogen bond acceptor site in the disulfide or peroxide molecule.     

Regulating function of methyl group on the strength of dihydrogen bond in HBeH-HCCH and HMgH-HCCH complexes

The regulating function of methyl group on the strength of dihydrogen bond was investigated in HBeH-HCCH and HMgH-HCCH complexes at the MP2/6-311++G(3df,2p) level. The bond lengths, infrared spectra, interaction energies, and charge transfers were analyzed. The presence of methyl group in the proton acceptor enhances the strength of dihydrogen bond, whereas its presence in the proton donor weakens the strength of dihydrogen bond. The charge analyses indicate that the methyl group in the proton donor and acceptor is electron-donating, thus the methyl group in the proton donor plays a negative role, whereas in the proton acceptor it plays a positive role in the formation of dihydrogen bond.     

Theoretical study of the interaction between LiNH2 and HMgH

The lithium bond between HMgH and LiNH₂ has been predicted and characterized with quantum chemical calculations at the MP2/6‐311++G(d,p) level. Upon formation of the lithium bond, both the Mg? H and Li? N bonds are stretched. The Li? N bond undergoes a red shift, whereas the Mg? H bond exhibits a blue shift. The lithium‐bonded complex is controlled mainly by electrostatic and polarization interactions. The binding energy of HMgH with LiNH₂ is computed to be 12.47 kcal/mol. The binding of the two molecules is enhanced by the substitution with the methyl group in the Li acceptor, whereas it is weakened by the replacement with whether the electron‐withdrawing group such as F, Cl, CN, NC, or the electron‐donating group (OH and HN₂). A negative cooperativity is present in the ternary system of 2LiNH₂ and HMgH. The polarization interaction plays an important role in the negative cooperativity. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Hydrogen bond of radicals: Interaction of HNO with HCO,HNO, and HOO

Ab initio quantum mechanics methods are employed to investigate hydrogen bonding interactions between HNO and HCO, HOO radicals, and closed‐shell HNO. The systems were calculated at MP2/6‐311++G (2d, 2p) level and G2MP2 level. The topological and NBO analysis were investigated the origin of hydrogen bonds red‐ or blue‐shifts. In addition, the comparisons were performed between HNO‐opened‐shell radical (HCO, HOO) complexes and HNO‐corresponding closed‐shell molecule (H₂CO, HOOH) complexes. It is found that the stabilities of complexes increase from HNO‐HCO to HNO‐HOO. There are blue‐shifts of N? H, C? H stretching vibrational frequencies and a red‐shift of O? H stretching vibrational frequency in the complexes. Rehybridization and electron density redistribution contribute to the blue‐shifts of C? H and N? H stretching vibrational frequencies. Compared with the closed‐shell H₂CO, HCO is weaker proton donor and weaker proton acceptor. For the HOO, it is stronger proton donor and weaker proton acceptor than the HOOH is. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

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.     

Nonadditivity of methyl group in single‐electron hydrogen bond of methyl radical‐water complex

The nonadditivity of methyl group in the single‐electron hydrogen bond of the methyl radical‐water complex has been studied with quantum chemical calculations at the UMP2/6‐311++G(2df,2p) level. The bond lengths and interaction energies have been calculated in the four complexes: CH₃? H₂O, CH₃CH₂? H₂O, (CH₃)₂CH? H₂O, and (CH₃)₃C? H₂O. With regard to the radicals, tert‐butyl radical forms the strongest hydrogen bond, followed by iso‐propyl radical and then ethyl radical; methyl radical forms the weakest hydrogen bond. These properties exhibit an indication of nonadditivity of the methyl group in the single‐electron hydrogen bond. The degree of nonadditivity of the methyl group is generally proportional to the number of methyl group in the radical. The shortening of the C···H distance and increase of the binding energy in the (CH₃)₂CH? H₂O and (CH₃)₃C? H₂O complexes are less two and three times as much as those in the CH₃CH₂? H₂O complex, respectively. The result suggests that the nonadditivity among methyl groups is negative. Natural bond orbital (NBO) and atom in molecules (AIM) analyses also support such conclusions. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

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.     

Structural properties and nonlinear optical responses of superatom compounds BF4‐M (M = Li,FLi2, OLi3, NLi4)

A new type of superhalogen‐(super)alkali compound, BF₄‐M (M = Li, FLi₂, OLi₃, NLi₄), is theoretically characterized at the MP2/6‐311+G(3df) level. The interaction between superhalogen BF₄ and different shaped (super)alkali M is found to be strong and ionic in nature. Bond energies of these BF₄‐M species are in the range of 200.0–226.7 kcal/mol at the CCSD(T)/6‐311+G(3df) level, which are much larger than the traditional ionic bond energy of 130.1 kcal/mol of FLi. In addition, different from the alkali halides, the BF₄‐M compounds prefer to dissociate into ions rather than neutral fragments. The energetic properties of BF₄‐M are found to be closely related to the size of the M subunit. The different effects of superalkali and superhalogen subunits on the nonlinear optical (NLO) properties of such superatom compounds are also revealed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Examination of the structures,energetics, and vibrational frequencies of small sulfur-containing prototypical dimers, (H2S)2 and H2O/H2S

The optimized geometries, vibrational frequencies, and dissociation energies from MP2 and CCSD(T) computations with large correlation consistent basis sets are reported for (H₂S)₂ and H₂O/H₂S. Anharmonic vibrational frequencies have also been computed with second-order vibrational perturbation theory (VPT2). As such, the fundamental frequencies, overtones, and combination bands reported in this study should also provide a useful road map for future spectroscopic studies of the simple but important heterogeneous H₂O/H₂S dimer in which the hydrogen bond donor and acceptor can interchange, leading to two unique minima with very similar energies. Near the CCSD(T) complete basis set limit, the HOH⋯SH₂ configuration (H₂O donor) lies only 0.2 kcal mol⁻¹ below the HSH⋯OH₂ structure (H₂S donor). When the zero-point vibrational energy is included, however, the latter configuration becomes slightly lower in energy than the former by <0.1 kcal mol⁻¹. © 2018 Wiley Periodicals, Inc.     

Regular/abnormal variation in the strength and nature of the halogen bond between H2Te and the dihalogens: Prominent effect of methyl substituents

The halogen-bonded complexes between H₂Te/Me₂Te and the dihalogen molecules XY (XY = F₂, Cl₂, Br₂, I₂, ClF, ClBr, BrF, BrCl, BrI, IF, ICl, IBr) have been studied to investigate the dependence of its strength and nature on the halogen donor X and its adjoining atom Y, as well as the methyl groups in the electron donor. The interaction energy varies between −1.7 and − 43.5 kcal/mol, indicating that the Te atom in H₂Te/Me₂Te has a strong affinity for the dihalogen molecules. For the H₂Te-XY complex, the halogen bond is stronger for the heavier halogen donor X atom and the strong electron-withdrawing group Y. However, for Me₂Te-XY, the halogen bond is stronger for the lighter halogen donor X atom. The H₂Te/Me₂Te-F₂ complex has the largest interaction energy, although the σ-hole on F₂ is the smallest in magnitude. In most of the complexes, the electrostatic and polarization contributions to the binding strength are similar in magnitude. However, for H₂Te/Me₂Te-F₂, the polarization contribution is much larger than the electrostatic contribution, with a significant contribution from charge transfer.     

7‐Methoxy‐1H‐indazole,a new inhibitor of neuronal nitric oxide synthase

The crystal structure of 7‐methoxy‐1H‐indazole, C₈H₈N₂O, an inhibitor of nitric oxide synthase, shows that the methoxy group lies in the plane of the indazole system with its methyl group located trans to the indazole N—H group. The crystal packing consists principally of hydrogen‐bonded trimers. Intermolecular hydrogen‐bonding interactions are formed between the indazole N atoms, with the N—H group as a hydrogen‐bond donor and the remaining N atom as an acceptor.     

Conformational preference and mechanism of decarboxylation of levodopa. A quantum dynamics/quantum mechanics study

The present study addresses the conformational preferences and the mechanism of decarboxylation of levodopa (LD). LD is used to increase dopamine concentrations in the treatment of Parkinson's disease. LD crosses the protective blood–brain barrier, where it is converted into dopamine by the process of decarboxylation. Molecular dynamics simulation has been carried out at the DFT/6‐31++G level of theory to identify the global minimum structure of LD. Conformational preferences of the amino acid side chain of LD has been investigated at the B3LYP/6‐311++G** level of theory. Fourier transform analysis has been performed to identify the origin of the rotational barriers. Electrostatic dipole moment and bond interactions underlie the observed potential energy barriers for rotation of the amino acid side chain of LD. The vital biological process of decarboxylation of LD has been examined in the gas phase and in aqueous solution. Without the presence of water, there is only one possible route for the decarboxylation of LD. In this concerted mechanism, a proton transfer and breakage of the C₁₀—C₁₈ bond, take place simultaneously (ΔE^# = 73.2 kcal/mol). In solution, however, two possible decarboxylation routes are available for LD. The first involve the formation of a zwitterionic intermediate (ΔE^# = 72.4 kcal/mol). The zwitterionic form of LD have been localized using explicitly bound water molecules to model short‐range solvent effects and self‐consistent reaction field polarized continuum model to estimate long‐range solvent interactions. The second route involve the formation of a cyclic structure in which a water molecule acts as a bridge linking the anticarboxylic hydrogen and α‐position carbon atom (ΔE^# = 59.8 kcal/mol). Natural bond orbital (NBO) analysis reveals that the conformational and overall stability of the amino acid side chain is facilitated by the antiperiplanar interactions between the phenyl moiety C—H and C—C bonds and C—X bonds of the amino acid side chain. However, much of the major donor–acceptor interactions is of the lone pair type and is localized within the amino acid side chain itself. Results of the present work reveal that NBO data reflect nicely and identify clearly reaction coordinates at the transition species. © 2013 Wiley Periodicals, Inc.     

Structures and Electronic Properties of HOCl···HCOCl Complexes

B3LYP/6-311++G** and MP2/6-311++G** calculations were used to analyze the interaction between hypochlorous acid (HOCl) and formyl chloride (HCOCl). The results showed that there were four equilibrium geometries (S1, S2, S3, and S4) optimized at B3LYP/6-311++G** level, and all the equilibrium geometries were confirmed to be in stable states by analytical frequency calculations. Complexes S1 and S3 use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift hydrogen bond systems. However, the blue-shifted hydrogen bond (2C-3H···6O) coexists with 4Cl···5O interaction in structures S2. As for S4, it uses the 7Cl atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift halogen bond system. Interaction energies between monomers in the four complexes corrected with basis set superposition error (BSSE) and zero-point vibrational energy (ZPVE) lie in the range from −5.05 to −14.76 kJ·mol⁻¹ at MP2/6-311++G** level. The natural bond orbital (NBO) and atoms in molecules (AIM) theories have also been applied to explain the structures and the properties of the complexes.     

Cooperativity between the Halogen Bond and the Hydrogen Bond in H3N⋅⋅⋅XY⋅⋅⋅HF Complexes (X,Y=F,Cl, Br)

Ab initio calculations are used to provide information on H₃N???XY???HF triads (X, Y=F, Cl, Br) each having a halogen bond and a hydrogen bond. The investigated triads include H₃N???Br₂‐HF, H₃N???Cl₂???HF, H₃N???BrCI???HF, H₃N???BrF???HF, and H₃N???ClF???HF. To understand the properties of the systems better, the corresponding dyads are also investigated. Molecular geometries, binding energies, and infrared spectra of monomers, dyads, and triads are studied at the MP2 level of theory with the 6‐311++G(d,p) basis set. Because the primary aim of this study is to examine cooperative effects, particular attention is given to parameters such as cooperative energies, many‐body interaction energies, and cooperativity factors. The cooperative energy ranges from ?1.45 to ?4.64 kcal mol^?1, the three‐body interaction energy from ?2.17 to ?6.71 kcal mol^?1, and the cooperativity factor from 1.27 to 4.35. These results indicate significant cooperativity between the halogen and hydrogen bonds in these complexes. This cooperativity is much greater than that between hydrogen bonds. The effect of a halogen bond on a hydrogen bond is more pronounced than that of a hydrogen bond on a halogen bond.     

Interaction energy and the shift in OH stretch frequency on hydrogen bonding for the H2O → H2O,CH3OH → H2O,and H2O → CH3OH dimers

The ability to use calculated OH frequencies to assign experimentally observed peaks in hydrogen bonded systems hinges on the accuracy of the calculation. Here we test the ability of several commonly employed model chemistries—HF, MP2, and several density functionals paired with the 6‐31+G(d) and 6‐311++G(d,p) basis sets—to calculate the interaction energy (D_e) and shift in OH stretch fundamental frequency on dimerization (δ(ν)) for the H₂O → H₂O, CH₃OH → H₂O, and H₂O → CH₃OH dimers (where for X → Y, X is the hydrogen bond donor and Y the acceptor). We quantify the error in D_e and δ(ν) by comparison to experiment and high level calculation and, using a simple model, evaluate how error in D_e propagates to δ(ν). We find that B3LYP and MPWB1K perform best of the density functional methods studied, that their accuracy in calculating δ(ν) is ≈ 30–50 cm^?1 and that correcting for error in D_e does little to heighten agreement between the calculated and experimental δ(ν). Accuracy of calculated δ(ν) is also shown to vary as a function of hydrogen bond donor: while the PBE and TPSS functionals perform best in the calculation of δ(ν) for the CH₃OH → H₂O dimer their performance is relatively poor in describing H₂O → H₂O and H₂O → CH₃OH. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Long‐range π‐type hydrogen bond in dimers CH2?HF,CH2O?H2O,and CH2O?NH3

Using four basis bets, (6‐311G(d,p), 6‐31+G(d,p), 6‐31++G(2d,2p), and 6‐311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for the dimers CH₂O? HF, CH₂O? H₂O, CH₂O? NH₃, and CH₂O? CH₄. The structures of CH₂O? HF, CH₂O? H₂O, and CH₂O? NH₃ are cycle‐shaped, which result from the larger bend of σ‐type hydrogen bonds. The bend of σ‐type H‐bond O…H? Y (Y?F, O, N) is illustrated and interpreted by an attractive interaction of a chemically intuitive π‐type hydrogen bond. The π‐type hydrogen bond is the interaction between one of the H atoms of CH₂O and lone pair(s) on the F atom in HF, the O atom in H₂O, or the N atom in NH₃. In contrast with the above three dimers, for CH₂O? CH₄, because there is not a π‐type hydrogen bond to bend its linear hydrogen bond, the structure of CH₂O? CH₄ is noncyclic shaped. The interaction energy of hydrogen bonds and the π‐type H‐bond are calculated and discussed at the CCSD (T)/6‐311++G(3df,3pd) level. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

气相中O3与HSO自由基间的氢键复合物

气相中O3与HSO自由基之间的相互作用及其反应在大气化学中非常重要.在DFT-B3LYP/6-311++G**和MP2/6-311++G**水平上求得O3+HSO复合物势能面上的稳定构型,B3LYP方法得到了三种构型(复合物Ⅰ,Ⅱ和Ⅲ),而MP2方法只能得到一种构犁(复合物Ⅱ).在复合物Ⅰ和Ⅲ中,HSO单元中的1H原子作为质子供体.与O3分子中的端基O原子作为质子受体相互作用,形成红移氢键复合物;而在复合物Ⅱ中,虽与复合物Ⅰ和Ⅲ中具有相间的质子供体和质子受体,却形成了蓝移氢键复合物.B3LYP/6-311++G**水平上计算的单体间相互作用能的计算考虑了基组重甍误差(BSSE)和零点振动能(ZPVE)校正,其值在-3.37到-4.55 kJ·mol-1之间.采用自然键轨道理论(NBO)对单体间相互作用的本质进行了考查,并通过分子中原子理论(AIM)分析了三种复合物中氢键的电子密度拓扑性质.     

Molecular orbital theory of the hydrogen bond. VIII. Hydrogen bonding in H2OH2CO in relaxed singlet and triplet n → π* states

Ab initio SCF CI calculations with a minimal STO-3G basis set have been performed on the hydrogen bonded dimers in which H₂O is the proton donor to H₂CO in its relaxed singlet and triplet n→π^* states. Two dimers which are easily interconverted are found in the singet n→π^* state with hydrogen bond energies of 1.82 and 1.71 kcal/mole. The equilibrium dimer in the triplet state has a hydrogen bond energy of 2.97 kcal/mole. In both states, hydrogen bond formation occurs at the carbon atom. The structures of the dimers and the nature of the intermolecular surfaces in the regions of hydrogen bond formation are examined. Electron densities and distributions are also discussed.     

Conformational Study of α‐N‐Acetyl‐D‐Neuraminic Acid by Density Functional Theory

The stable structures of α‐N‐acetyl‐D‐neuraminic acid (Neu5Acα) in the gas phase were studied at the B3LYP level of theory using 6‐31G(d,p) and 6‐31++G(d,p) basis sets. They are classified into five types according to the patterns of the intramolecular hydrogen bond formations. One of the stable structures had intramolecular hydrogen bond network of O₉H_O9 … O₈H_O8 … O?C₁‐O₁H_O1 and O₇H_O7…O?CHN‐C₅ similar to the crystal structure of Neu5Ac‐α‐methyl glycoside methyl ester. The stable structures of Neu5Acα are reasonable for the following sialooligosaccharide ligand studies with respect to the relationship between OH group orientations and intramolecular hydrogen bond formations. The barrier heights for isomerizations between the stable structures were computed to be 2.8 to 6.7 kcal/mol at the B3LYP/6‐31++G(d,p)//B3LYP/6‐31G(d,p) level, which are basic factors for the conformational behavior of Neu5Acα before its interactions with receptors. We also calculated Neu5Acα–4 or 5‐water complexes to take account of the solvent effect on the intramolecular hydrogen bonds in the stable structures. Consequently, the structures of Neu5Acα in the complexes are similar to each other, which is consistent with the known NMR data. Thus, the optimum Neu5Acα‐water complexes are some of the reasonable pseudohydrous Neu5Acα.