Hydrogen bond nature in formamide (CYHNH2···XH; YO,S, Se,Te; XF,HO, NH2) complexes at their ground and low‐lying excited states

A theoretical study on the nature of hydrogen bond for formamide and its heavy complexes (CYHNH₂···XH; Y?O, S, Se, Te; X?F, HO, NH₂) was performed on the basis of density functional theory and the quantum chemistry analysis. Except for the CYHNH₂···NH₃ complexes, the substitution of O atom at formamide with less electronegative atoms (S, Se, and Te) is found to weaken the hydrogen bond (H‐bond). This substitution results in cyclic structure of hydrated and ammoniated formamide complexes by the formation of bifunctional H‐bonds (Y···H₄X; X···H₃C). Natural bond orbital analysis indicates that the H‐bond is weakened because of less charge transfer from a lone pair orbital of H‐bond acceptor to antibonding orbital of H‐bond donor. The quantum theory of atoms in molecules analysis reveals that the acyclic structure with single H‐bond stabilizes the complexes more than the cyclic structure formed by bifunctional H‐bonds. Natural energy decomposition analysis (NEDA) and block‐localized wavefunction energy decomposition (BLW‐ED) analyses show that the H‐bond stabilization energies of NEDA and BLW‐ED have good correlation with the dissociation energy of formamide complexes and charge transfer from donor to acceptor atom play an important role in H‐bonding. We have also studied the low‐lying electronic excited states (T₁, T₂, and S₁) for CYHNH₂···H₂O complexes to explore the nature of H‐bond on the basis of electronegativity and found that NEDA also establishes a good correlation with relative electronic energy (with respect to their ground state) and H‐bond strength at their excited states. Copyright © 2014 John Wiley & Sons, Ltd.     

Intra‐ and intermolecular N?H···O hydrogen bonds in pyrrolyl derivatives of indane‐1,3‐dione – experimental and theoretical study

2‐(Pyrrol‐2‐ylmethylene)‐1,3‐indandione ( 4 ) and 2‐(pyrrol‐2‐ylmethylene)‐3‐dicyanomethylidene‐1‐indanone ( 5 ) were synthesized. Multinuclear and 2D‐NMR, IR, UV spectroscopic investigations as well as quantum chemical calculations showed the presence of strong hydrogen bonding in these molecules. For both molecules, the presence of two conformers, with and without H‐bond, was experimentally detected in the basic solvents (DMSO, acetone, pyridine) and the solvate complexes were theoretically calculated. Specific behavior of the intramolecular H‐bonded complexes different from that of the intermolecular H‐complexes is discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Theoretical study of cooperativity between hydrogen bond‒hydrogen bond,halogen bond‒halogen bond and hydrogen bond‒halogen bond in ternary FX…diazine…XF (X = H and Cl) complexes

ABSTRACT

In the present work, the cooperativity between hydrogen bond?hydrogen bond, halogen bond?halogen bond and hydrogen bond?halogen bond in ternary FX…diazine…XF (X = H and Cl) complexes is theoretically investigated. The sign of cooperative energy (E_coop) obtained in all of the triads is positive which indicates that the ternary complex is less stable than the sum of the two isolated binary complexes. Moreover, our calculations show that E_coop value in triads increases as FX…pyridazine…XF > FX…pyrimidine…XF > FX…pyrazine…XF. In agreement with energetic, geometrical and topological properties, electrostatic potentials and coupling constants across ¹⁵N…X?¹⁹F (X = ¹H or ³⁵Cl) hydrogen and halogen bonds indicate that hydrogen and halogen bonds are weakened in the considered complexes where two hydrogen and halogen bonds coexist. As compared to N…H hydrogen bond, it is also observed that cooperativity has greater effect on N…Cl halogen bond.     

Cooperative effects between tetrel bond and other σ–hole bond interactions: a comparative investigation

Covalently bonded atoms of Groups IV–VII tend to have anisotropic charge distributions, the electronic densities being less on the extensions of the bonds (σ–holes) than in the intervening regions. These σ–holes often give rise to positive electrostatic potentials through which the atom can interact attractively and highly directionally with negative sites. In this work, cooperative effects between tetrel bond and halogen/chalcogen/pnicogen bond interactions are studied in multi-component YH₃M···NCX···NH₃ complexes, where Y = F, CN; M = C, Si and X = Cl, SH and PH₂. These effects are analysed in detail in terms of the structural, energetic, charge-transfer and electron density properties of the complexes. The nature of the σ–hole bonds is unveiled by quantum theory of atoms in molecules and natural bond orbital theory. A favourable cooperativity is found with values that range between ?0.34 and ?1.15 kcal/mol. Many-body decomposition of interaction energies indicate that two-body energy term is the most important source of the attraction, which its contribution accounts for 87%–96% of the total interaction energy.     

Hydrogen bond and internal rotations barrier: DFT study on heavier group‐14 analogues of formamide

A theoretical study on heavier group‐14 substituting effect on the essential property of formamide, strong hydrogen bond with water and internal rotational barrier was performed within the framework of natural bond orbital (NBO) analysis and based on the density functional theory calculation. For heavier group‐14 analogues of formamide (YHONH₂, Y = Si, Ge and Sn), the n_N–π_Y=O conjugation strength does not always reduce as Y becomes heavier, for example, silaformamide and germaformamide have similar strength of delocalization. Heavier formamides prefer being H‐bond donors to form FYO–H₂O complexes to being H‐bond acceptors to form FYH–H₂O complexes. The NEDA analysis indicates that H‐bond energies of FYO–H₂O complexes increase as moving down group 14 due to concurrently stronger charge transfer (CT) and electrostatic attraction and for the FYH–H₂O complexes H‐bond strengths are similar. The model of CTs from FYO to H₂O differs from that at FYH–H₂O complexes, which are contributed not only by aligning lone‐pair orbital of O but also by another lone‐pair orbital. At two lowest lying excited states (the triplet and S₁ excited states), formamide and its heavier analogues form double H‐bonds with H₂O molecule at the same time. The barrier heights of internal rotation become gradually low from C to Sn, formamide (15.73 kcal/mol) > silaformamide (11.73 kcal/mol) > germaformamide (9.45 kcal/mol) > stannaformamide (7.50 kcal/mol) at the CCSD(T)/aug‐cc‐pVTZ//B3LYP/cc‐pVTZ level. NBO analysis indicates that the barrier does not only come from the n_N→π*_YO conjugation, and for heavier analogues of formamide, the n_N→σ*_YO hyperconjugation effect and steric effect considerably contribute to the overall rotational barrier. Copyright © 2013 John Wiley & Sons, Ltd.     

Intermolecular H‐bond in propan‐2‐ol and its solutions with acetonitrile

Formation of propan‐2‐ol–acetonitrile dimers is manifested in the Raman spectra as an appearance of a band of aggregates in the high‐wavenumber side of the CN vibrational band of liquid acetonitrile (∼2 cm⁻¹). The intensity of the band of aggregates changes with a change in the concentration of the mixture (1–0.05 mole fraction). For propan‐2‐ol we carried out nonempirical calculations of a structure of isolated dimer aggregates. The formation of an intramolecular H‐bond between the H and the O atom of the \newbox\osprulebox \newdimen\osprulewd \def\osprule#1#2{ \global\setbox\osprulebox=\hbox{#1} \osprulewd=\wd\osprulebox\advance\osprulewd by ‐8pt \raise0.5pc\hbox{$\matrix{\hskip‐1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr \noalign{\vskip‐1pt} \hbox{#1}\cr}$} } $\osprule{{\rm HCO}}{2.5} \hbox{H}$ group of length 2.045 Å is possible in the monomer molecule. The CH₃ groups of alcohol are not equivalent. In the dimer formation, intramolecular H‐bond in the \newbox\osprulebox \newdimen\osprulewd \def\osprule#1#2{ \global\setbox\osprulebox=\hbox{#1} \osprulewd=\wd\osprulebox\advance\osprulewd by ‐8pt \raise0.5pc\hbox{$\matrix{\hskip‐1pt\lower6.5pt\hbox{\vrule height #2pt}\lower4.5pt\hbox to \osprulewd{\hrulefill}\lower6.5pt\hbox{\vrule height #2pt}\cr \noalign{\vskip‐1pt} \hbox{#1}\cr}$} } $\osprule{{\rm HCO}}{2.5} \hbox{H}$ group is preserved. An intermolecular H‐bond of length 2.045 Å and energy 15 kJ/mole is formed between the H atom of one molecule and the O atom of another molecule of the O H. The length and energy of the H‐bond for the propan‐2‐ol–acetonitrile dimer formations calculate to 2.27 Å and 12.9 kJ/mole, respectively. The H‐bond is formed by σ‐electrons of nitrogen. The experimental data and the results of calculations are in good agreement. Copyright © 2007 John Wiley & Sons, Ltd.     

Cooperativity effects between σ-hole interactions: a theoretical evidence for mutual influence between chalcogen bond and halogen bond interactions in F2S···NCX···NCY complexes (X = F,Cl, Br,I; Y = H,F, OH)

Quantum chemical calculations are performed to study the cooperativity effects between chalcogen bond and halogen bond interactions in F₂S···NCX···NCY complexes, where X = F, Cl, Br, I and Y = H, F, OH. These effects are investigated in terms of geometric and energetic features of the complexes, which are computed by second-order Møller–Plesset perturbation theory (MP2). For each F₂S···NCX···NCY complex studied, the effect of cooperativity on the chalcogen bond is dependent on the strength of halogen bond. The results indicate that the interaction energies of chalcogen and halogen bonds in the triads are more negative relative to the respective dyads. The interaction energy of chalcogen bond is increased by 31%–49%, whereas that of halogen bond by 28%–62%. The energy decomposition analysis reveals that electrostatic force plays a main role in the cooperativity effects between the chalcogen bond and halogen bond interactions. The topological analysis, based on the quantum theory of atoms in molecules, is used to characterise the interactions and analyse their enhancement with varying electron density at bond critical points.     

Experimental (FT‐IR) and theoretical (DFT) studies on prototropy and H‐bond formation for pyrazine‐2‐amidoxime

The results of the first structural studies (with the use of both experimental and theoretical methods) on pyrazine‐2‐amidoxime (PAOX) were shown and discussed. FT‐IR spectra were recorded in different concentrations of the PAOX in apolar solvent to check the possibility of the inter‐ or intramolecular hydrogen‐bond formation. All possible tautomers–rotamers of PAOX were then theoretically considered at the DFT(B3LYP)/6‐311+G** level in vacuo. For selected isomers, calculations were also performed at higher levels of theory {B3LYP/6‐311+G(3df,2p) and G3B3}. Based on the results of DFT calculations, the most stable isomers were found, and their total free energies and infrared spectra were calculated. The energy variation plots for the N8?C7?N9?O10 and N1?C2?C7?N9 dihedral angles were also computed to find two energy barriers, one for E/Z isomerization around the C7?N9 double bond and the other one for rotation of the pyrazinyl ring around the C2?C7 single bond. The results show that the stability of the PAOX isomers strongly depend on their configuration and orientation of the substituents. The possibilities of inter‐ and intramolecular hydrogen bonds were also experimentally and theoretically checked. Finally, a potential of mean force was determined in CHCl₃ for a dimer of PAOX with hexamethylphosphoramide. Both, experimental and theoretical results are in agreement. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of complexation on the spectral and luminescent properties and photolysis of methyl[(4-aminophenyl)sulfonyl]carbamate

The spectral and luminescent properties and the photolysis of 1: 3 hydrogen bonded complexes of methyl[(4-aminophenyl)sulfonyl]carbamate (asulam) with water are studied with the aid of methods of quantum chemistry using the theory of intramolecular photophysical processes. It is shown that the formation of hydrogen bonds does not have a large effect on the spectral and luminescent properties of asulam. The breaking of the C-S and N-S bonds occurs according to the predissociation mechanism in electronically excited states localized on the bonds to be broken. In singlet photodissociative states, the N-S bond is more likely to break than the C-S bond, with the bond breaking being independent of the excitation energy. The formation of hydrogen bonded complexes increases the rate of population of photodissociative states, and, therefore, one can assume that the photoreaction efficiency increases.     

利用电子结构数据拟合H2分子的电子壳模型势函数参数

电子壳模型势函数在离子晶体的原子级计算机模拟中有广泛应用,其势参数主要通过拟合晶体的实验数据或电子结构数据得到.提出了通过拟合双原子分子的量子化学从头计算电子结构数据来获得该势函数的方法,并由H2分子的电子结构数据建立了H原子间的电子壳模型势函数.此外,还应用该势函数对H+2分子离子进行了计算.该势函数拟合方案更适合于共价键型的分子.     

An ab initio study on the nature of σ-hole interactions in pnicogen-bonded complexes with carbene as an electron donor

ABSTRACT

A theoretical study of the complexes formed between ZH₂X (Z = P, As, Sb, Bi; X = F, Cl, Br, CN, NC, OH, NH₂) and an N-heterocyclic carbene (imidazol-2-ylidene) is carried out by means of ab initio calculations. According to molecular electrostatic potential analysis, it is inferred that the divalent C atom of the carbene can act as a Lewis base with the pnicogen atom Z of ZH₂X. The pnicogen bond distances (Z–C) are in the range of 2.050–2.911 for these complexes. While the Z?X bonds are longer than the corresponding Z?C bonds in the X = Cl and Br complexes, most of the Z?X bonds are short enough to suggest that they should be considered as covalent bonds which have lost some degree of covalency. For a given Z, the ZH₂Br forms the strongest complex, followed by ZH₂Cl and ZH₂F. On the other hand, the binding energy in the halogenated ZH₂X complexes follows the reverse ranking expected based on the values of the σ-hole of the isolated ZH₂X monomers. The nature of the pnicogen bond interaction in these complexes is analysed by quantum theory of atoms in molecules (QTAIM) and natural bond orbital methods. According to QTAIM analysis, a partially covalent character can be attributed to the pnicogen bonds studied here.     

The hydrogen bond under pressure

The hydrogen bonds are quite pervasive in several classes of materials. Its parameters are known to show systematic variations with hydrogen bond length, and pressure variable is thus a natural way for studying hydrogen bonded substances. In this article, we review the unifying features as obtained through several experimental and theoretical investigations. Amongst other things, it is examined whether the observed pressure-induced variations in parameters of hydrogen bonds are consistent with the co-relations known on different chemical substances at normal pressure. In particular, the controversies on variations of O–H and H- - -O pairs with pressure and symmetrization of hydrogen bond have been resolved. The effects of close packing promoted by pressure such as formation of muli-centered hydrogen bonds and steric repulsions and the way the hydrogen bonds counter these in different ways are also examined.     

Symmetric bifurcated halogen bonds: substituent and cooperative effects

ABSTRACT

The aim of this study is to investigate the geometries, interaction energies and bonding properties of the symmetrical bifurcated halogen bond interactions (BXBs) by means of ab initio calculations. For this purpose, the NCX (X = Cl, Br) molecule is paired with a series of N-formyl formamide (NFF) derivatives (NFF-Z, Z = H, CN, CCH, OH, CH₃ and Li), and the properties of the resulting complexes are studied by molecular electrostatic potential, quantum theory of atoms in molecules, noncovalent interaction index and natural bond orbital analyses. For a fixed NCX molecule, interaction energies increase in the order of Z = Li > CH₃ > H > OH > CCH > CN. We found a strong correlation between the interaction energies of NCX:NFF-Z complexes and molecular electrostatic potential minimum values associated with NFF-Z monomers. Moreover, cooperative effects between BXB and X???N halogen bond interactions are studied in the ternary NCX:NCX:NFF-Z systems. Our results indicate that the strength of BXB interactions in the ternary complexes is enhanced by the presence of X???N bonds. Besides, cooperativity effects tend to increase the covalency of BXBs in these systems.     

Prediction models for the Abraham hydrogen bond donor strength: comparison of semi‐empirical,ab initio,and DFT methods

Hydrogen bonding has a great impact on the partitioning of organic compounds in biological and environmental systems as well as on the shape and functionality of macromolecules. Electronic characteristics of single molecules, localized at the H‐bond (HB) donor site, are able to estimate the donor strength in terms of the Abraham parameter A. The quantum chemically calculated properties encode electrostatic, polarizability, and charge‐transfer contributions to hydrogen bonding. A recently introduced respective approach is extended to amides with more than one H atom per donor site, and adapted to the semi‐empirical AM1 scheme. For 451 organic compounds covering acidic ? CH, ? NH? , and ? OH groups, the squared correlation coefficient is 0.95 for the Hartree–Fock and density functional theory (B3LYP) level of calculation, and 0.84 with AM1. The discussion includes separate analyses for weak, moderate, and strong HB donors, a comparison with the performance of increment methods, and opportunities for consensus modeling through the combined use of increment and quantum chemical methods. Copyright © 2011 John Wiley & Sons, Ltd.     

Exploring hydride-π interactions and their tuning by σ-hole bonds: an ab initio study

In the present work, ab initio calculations are performed to investigate the geometry, interaction energy and bonding properties of binary complexes formed between metal-hydrides HMX (M = Be, Mg, Zn and X = H, F, CH₃) and a series of π-acidic heteroaromatic rings. In all the resulting complexes, the heteroaromatic ring acts as a Lewis acid (electron acceptor), while the H atom of the HMX molecule acts as a Lewis base (electron donor). The nature of this interaction, called ‘hydride-π’ interaction, is explored in terms of molecular electrostatic potential, non-covalent interaction, quantum theory of atoms in molecules and natural bond orbital analyses. The results show that the interaction energies of these hydride-π interactions are between ?1.24 and ?2.72 kcal/mol. Furthermore, mutual influence between the hydride-π and halogen- or pnicogen-bonding interactions is studied in complexes in which these interactions coexist. For a given π-acidic ring, the formation of the pnicogen-bonding induces a larger enhancing effect on the strength of hydride-π bond than the halogen-bonding.     

Hydrogen‐bonded complexes of sulfonamides and thioamides with DMF: FT‐IR and DFT study,NBO analysis

The structure of H‐complexes of dimethylformamide (DMF) with N‐(2,2,2‐trichloro‐1‐hydroxyethyl)‐p‐toluenesulfonamide (1), N‐[1‐(4‐chlorophenylsulfonylamino)‐2,2,2‐trichloro)ethyl]dithiooxamide (2), N,N'‐bis[2,2‐dichloro‐1‐(4‐chlorophenylsulfonylamino)‐2‐phenylethyl]ethanebis(thioamide) (3) and N,N'‐bis[2,2,2‐trichloro‐1‐(phenylsulfonylamino)ethyl]ethanebis(thioamide) (3a) as proton donors was investigated using Fourier transform infrared spectroscopy and Density Functional Theory calculations. According to calculations, the interaction of DMF with the sulfonamide and thioamide NH groups in the complexes strongly affects the intramolecular H‐bonding in 1–3. From the natural bond orbital analysis, complexation with DMF strongly decreases the energy of the intramolecular N?H · · · S = C bonds, up to their rupture. Variation of the strength of the intra‐ and intermolecular H‐bonds in the complexes is consistent with the calculated frequencies of the NH and OH stretching vibrations, and the analysis of the corresponding bands in the IR spectra allows to suggest the preferable structure of the formed H‐complexes. Copyright © 2013 John Wiley & Sons, Ltd.     

A model of phase transitions in double-well Morse potential: Application to hydrogen bond

A model of phase transitions in double-well Morse potential is developed. Application of this model to the hydrogen bond is based on ab initio electron density calculations, which proved that the predominant contribution to the hydrogen bond energy originates from the interaction of proton with the electron shells of hydrogen-bonded atoms. This model uses a double-well Morse potential for proton. Analytical expressions for the hydrogen bond energy and the frequency of O–H stretching vibrations were obtained. Experimental data on the dependence of O–H vibration frequency on the bond length were successfully fitted with model-predicted dependences in classical and quantum mechanics approaches. Unlike empirical exponential function often used previously for dependence of O–H vibration frequency on the hydrogen bond length (Libowitzky, Mon. Chem., 1999, vol.130, 1047), the dependence reported here is theoretically substantiated.     

Hydrogen bonding in amylose/DMSO complexes studied by vibrational spectroscopy and density functional theory calculations

The intermolecular interactions in amylose/dimethyl sulfoxide (DMSO) complexes are discussed both experimentally and theoretically by means of Raman and infrared spectroscopies. The study is based on a preliminary analysis of well known systems such as pure liquid DMSO or DMSO in mixture with water: for such systems, an analysis of the CS stretching region is carried out both by means of Raman and infrared spectra. In particular, Raman spectra reveal a high sensitivity to the strength and to the type of interaction involving the DMSO molecules. These results, applied to the investigation of amylose‐DMSO complexes, show the presence of different hydrogen‐bonded complexes which coexist in this compound. In particular, DMSO molecules are identified both on the external surface of the V‐amylose helix, where they can interact via one hydrogen bond and in the inner channel of the helix where they can interact via two hydrogen bonds. The present findings open the possibility of applying vibrational spectroscopy to the characterization of inclusion compounds of amylose which are currently being involved in many fields of nanosciences. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of hydrogen and halogen bonds between dimethyl sulfoxide and hypohalous acid: competition and cooperativity

A theoretical study of the complexes formed between dimethyl sulfoxide (DMSO) and hypohalous acid (HOX, X = Cl, Br, and I) has been carried out at the MP2/aug-cc-pVTZ level. For each HOX, four minima binary complexes were found, two mainly with an OH???O hydrogen bond and the other two with an OX???O halogen bond. The hydrogen-bonded complexes are more stable than the halogen-bonded analogues for HOCl and HOBr, while both types of complexes have similar stability in the iodine case. A red shift was found for the associated H–O and X–O bond stretch vibrations and a small blue shift for the distant bonds. As the oxygen of DMSO simultaneously binds with two HOCl molecules, the corresponding interactions are weakened with diminutive effect. This diminutive effect is the largest in the complexes with two OH???O hydrogen bonds but the smallest in those with two OCl???O halogen bonds.