Ab Initio and Quantum Chemical Topology studies on the isomerization of HONO to HNO2. Effect of the basis set in QCT

The article focus on the isomerization of nitrous acid HONO to hydrogen nitryl HNO₂. Density functional (B3LYP) and MP2 methods, and a wide variety of basis sets, have been chosen to investigate the mechanism of this reaction. The results clearly show that there are two possible paths: 1) Uncatalysed isomerisation, trans‐HONO → HNO₂, involving 1,2‐hydrogen shift and characterized by a large energetic barrier 49.7 ÷ 58.9 kcal/mol, 2) Catalysed double hydrogen transfer process, trans‐HONO + cis‐HONO → HNO₂ + cis‐HONO, which displays a significantly lower energetic barrier in a range of 11.6 ÷ 18.9 kcal/mol. Topological analysis of the Electron Localization Function (ELF) shows that the hydrogen transfer for both studied reactions takes place through the formation of a ‘dressed’ proton along the reaction path. 1 Use of a wide variety of basis sets demonstrates a clear basis set dependence on the ELF topology of HNO₂. Less saturated basis sets yield two lone pair basins, V₁(N), V₂(N), whereas more saturated ones (for example aug‐cc‐pVTZ and aug‐cc‐pVQZ) do not indicate a lone pair on the nitrogen atom. Topological analysis of the Electron Localizability Indication (ELI‐D) at the CASSCF (12,10) confirms these findings, showing the existence of the lone pair basins but with decreasing populations as the basis set becomes more saturated (0.35e for the cc‐pVDZ basis set to 0.06e for the aug‐cc‐pVTZ). This confirms that the choice of basis set not only can influence the value of the electron population at the particular atom, but can also lead to different ELF topology. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

S−H…O and O−H…O Hydrogen Bonds-Comparison of Dimers of Thiocarboxylic and Carboxylic Acids

ωB97-XD/aug-cc-pVTZ calculations were performed on dimers of selected thiocarboxylic acids and on analogous carboxylic acids. The sample of calculated thiocarboxylic acids is an extension of the Cambridge Structural Database search that contains only a few such structures. The Natural Bond Orbital (NBO) method, Symmetry-Adapted Perturbation Theory (SAPT) approach, Non-Covalent Interaction (NCI) method and Quantum Theory of Atoms in Molecules (QTAIM) were applied additionally to analyse interactions in dimers of thiocarboxylic and carboxylic acids. The insights into crystal structures as well as into results of calculations show that the formation of S−H…O hydrogen bonds between molecules of thiocarboxylic acids is steered by the same mechanisms as the formation of much stronger O−H…O hydrogen bonds in carboxylic acids. The intramolecular O−H…O and C−H…S hydrogen bonds occurring in few considered structures are also analysed.     

A coupled cluster treatment of intramonomer electron correlation within symmetry-adapted perturbation theory: benchmark calculations and a comparison with a density-functional theory description

Symmetry-adapted perturbation theory (SAPT) with intramonomer electron correlation described by coupled cluster theory limited to single and double excitations was applied to 21 noncovalent complexes in their minimum geometries. The resulting benchmark contributions to the interaction energy were utilized to examine the accuracy of a more approximate variant of the SAPT method, where interacting molecules are described by density functional theory (DFT) with different functionals, like LDA, PBE, B3LYP, PBE0, M05, M05-2X, M06, and M06-2X (in all cases the asymptotic correction for the exchange-correlation functional has been utilized). Average errors for individual energy components of SAPT(DFT) are not larger than 10% for best functionals under study. Among the tested functionals PBE0, M05, and B3LYP should be especially recommended for the SAPT(DFT) approach. The M06 functional gives the largest errors with respect to SAPT(CCSD) and should not be used for describing intramonomer correlation in SAPT.     

噻吩与6种氢化物相互作用本质的从头算MP2研究

在从头算MP2/aug-cc-pVDZ理论水平上,研究了6种典型氢化物HnX（HCl、HF、H2O、H2S、NH3、PH3）与杂芳环噻吩（C4H4S）分子形成复合物的几何形状及其相互作用的本质。寻找到C4H4S与小分子氢化物形成的π型优势噻吩复合物。用对称匹配微扰理论（SPTA）和自然键轨道（NBO）理论,分析了该系列复合体系的能量及其分项。SPTA模拟计算结果表明,C4H4S系列6种小分子氢化物复合体系间的静电作用能和色散作用能贡献较大,是关键项,而分子间的诱导作用能的贡献占比较小。其中当X=F或O原子时,分子间静电相互作用能分项占比稍占优势,而当X=N,Cl,S和P原子时,则分子间色散相互作用能分项稍占优势。自然键轨道理论和电子局域密度函数图也支持以上结论。     

Revealing the physical nature and the strength of charge‐inverted hydrogen bonds by SAPT(DFT), MP2, SCS‐MP2, MP2C,and CCSD(T) methods

The physical nature of charge‐inverted hydrogen bonds in H₃XH YH₃ (X = Si, Ge; Y = Al, Ga) dimer systems is studied by means of the SAPT(DFT)‐based decomposition of interaction energies and supermolecular interaction energies based on MP2, SCS‐MP2, MP2C, and CCSD(T) methods utilizing dimer‐centered aug‐cc‐pCVnZ (n = D, T, Q) basis sets as well as an extrapolation to the complete basis set limit. It is revealed that charge‐inverted hydrogen bonds are inductive in nature, although dispersion is also important. Computed interaction energies form the following relation: . It is confirmed that the aug‐cc‐pCVDZ basis set performs poorly and that very accurate values of interaction and dispersion energies require basis sets of at least quadrupole‐ζ quality. Considerably large binding energies suggest potential usefulness of charge‐inverted hydrogen bonds as an important structural motif in molecular binding. Terminology applying to σ‐ and π‐hole interactions as well as to triel and tetrel bonds is discussed. According to this new terminology the charge‐inverted hydrogen bond would become the first described case of a hydride‐triel bond. © 2017 Wiley Periodicals, Inc.     

Highly accurate benchmark calculations of the interaction energies in the complexes C6H6···C6X6 (X = F,Cl, Br,and I)

Different from the case of the benzene dimer, the differences between the interaction energies are always less than 0.50 kcal/mol for face‐to‐face eclipsed, face‐to‐face staggered, and parallel‐displaced configurations of all investigated complexes C₆H₆···C₆X₆ (X = F, Cl, Br, and I). Hence, it is a great challenge for quantum chemists to accurately calculate the interaction energies for the three configurations of the complexes C₆H₆···C₆X₆. This work demonstrates that results obtained with the PBE0 density functional combined with the D3 dispersion correction (PBE0‐D3) and the basis set def2‐TZVPP are in excellent agreement with the estimates of the coupled‐cluster singles, doubles, and perturbative triples [CCSD(T)] complete basis set (CBS) limit. The other finding in this study is that, in comparison with the gold‐standard CCSD(T)/CBS benchmark, the spin‐component scaled (SCS) zeroth‐order symmetry‐adapted perturbation theory (SAPT0), when paired with the basis set aug‐cc‐pVDZ, performs also very well, and its performance is even better than that of the PBE0‐D3/def2‐TZVPP method or the conventional SAPT/aug‐cc‐pVQZ method. The findings of this study are very significant because both PBE0‐D3/def2‐TZVPP and SCS‐SAPT0/aug‐cc‐pVDZ can deal with the systems with more than 200 atoms.     

Theoretical Investigation of Carbon Dioxide Adsorption on Li+-Decorated Nanoflakes

Recently, the capture of carbon dioxide, the primary greenhouse gas, has attracted particular interest from researchers worldwide. In the present work, several theoretical methods have been used to study adsorption of CO₂ molecules on Li⁺-decorated coronene (Li⁺@coronene). It has been established that Li⁺ can be strongly anchored on coronene, and then a physical adsorption of CO₂ will occur in the vicinity of this cation. Moreover, such a decoration has substantially improved interaction energy (E_int) between CO₂ molecules and the adsorbent. One to twelve CO₂ molecules per one Li⁺ have been considered, and their E_int values are in the range from −5.55 to −16.87 kcal/mol. Symmetry-adapted perturbation theory (SAPT0) calculations have shown that, depending on the quantity of adsorbed CO₂ molecules, different energy components act as the main reason for attraction. AIMD simulations allow estimating gravimetric densities (GD, wt.%) at various temperatures, and the maximal GDs have been calculated to be 9.3, 6.0, and 4.9% at T = 77, 300, and 400 K, respectively. Besides this, AIMD calculations validate stability of Li⁺@coronene complexes during simulation time at the maximum CO₂ loading. Bader’s atoms-in-molecules (QTAIM) and independent gradient model (IGM) techniques have been implemented to unveil the features of interactions between CO₂ and Li⁺@coronene. These methods have proved that there exists a non-covalent bonding between the cation center and CO₂. We suppose that findings, derived in this theoretical work, may also benefit the design of novel nanosystems for gas storage and delivery.     

Exploring Intra- and Intermolecular Interactions in Selected N-Oxides—The Role of Hydrogen Bonds

Intra- and intermolecular interactions have been explored in selected N-oxide derivatives: 2-(N,N-dimethylamino-N-oxymethyl)-4,6-dimethylphenyl (1) and 5,5’-dibromo-3-diethylaminomethyl-2,2’-biphenol N-oxide (2). Both compounds possess intramolecular hydrogen bonding, which is classified as moderate in 1 and strong in 2, and resonance-assisted in both cases. Density Functional Theory (DFT) in its classical formulation as well as Time-Dependent extension (TD-DFT) were employed to study proton transfer phenomena. The simulations were performed in the gas phase and with implicit and explicit solvation models. The obtained structures of the studied N-oxides were compared with experimental data available. The proton reaction path was investigated using scan with an optimization method, and water molecule reorientation in the monohydrate of 1 was found upon the proton scan progress. It was found that spontaneous proton transfer phenomenon cannot occur in the electronic ground state of the compound 1. An opposite situation was noticed for the compound 2. The changes of nucleophilicity and electrophilicity upon the bridged proton migration were analyzed on the basis of Fukui functions in the case of 1. The interaction energy decomposition of dimers and microsolvation models was investigated using Symmetry-Adapted Perturbation Theory (SAPT). The simulations were performed in both phases to introduce polar environment influence on the interaction energies. The SAPT study showed rather minor role of induction in the formation of homodimers. However, it is worth noticing that the same induction term is responsible for the preference of water molecules’ interaction with N-oxide hydrogen bond acceptor atoms in the microsolvation study. The Natural Bond Orbital (NBO) analysis was performed for the complexes with water to investigate the charge flow upon the polar environment introduction. Finally, the TD-DFT was applied for isolated molecules as well as for microsolvation models showing that the presence of solvent affects excited states, especially when the N-oxide acceptor atom is microsolvated.     

Hydrogen sulphide H2S and noble gases (Ng = He,Ne, Ar,Kr, Xe,Rn) complexes: A theoretical study of their dynamics,spectroscopy, and interactions

In this work, some basic features of the intermolecular bond in gas phase H₂S-Ng complexes (Ng = He, Ne, Ar, Kr, Xe, and Rn) have been investigated in detail, coupling information from scattering experiments with results of quantum chemical calculations at the CCSD(T)/aug-cc-pVTZ level. Spectroscopic constants, rotovibrational energies, and lifetime as a function of temperature have been evaluated for the complete family of H₂S-Ng systems, and an extensive study of involved intermolecular interactions has been performed. In particular, their nature has been characterized by exploiting Atoms-In-Molecules (AIM), Non-Covalent Interactions (NCI), Symmetry-Adapted Perturbation Theory (SAPT), and Charge Displacement (CD) methods, and it was found that all complexes are bound essentially by near-isotropic van der Waals forces, perturbed by weak-stabilizing charge (electron) transfer contributions. Obtained results also show that these additional contributions increase from He up to Rn, providing an appreciable chemical-stabilizing effect of the noncovalent intermolecular bond for H₂S-heavier Ng systems.