Prediction and characterization of the HMgH⋯LiX (X = H, OH, F, CCH, CN, and NC) complexes: a lithium–hydride lithium bond
26 Mar 2009-Physical Chemistry Chemical Physics (The Royal Society of Chemistry)-Vol. 11, Iss: 14, pp 2402-2407
TL;DR: In the present paper, a new type of lithium bonding complex HMgHLiX (X = H, OH, F, CCH, CN, and NC) has been predicted and characterized and the Li-X harmonic vibrational stretching frequency is blueshifted and redshifted in the HMg HLiX complexes.
Abstract: In the present paper, a new type of lithium bonding complex HMgH⋯LiX (X = H, OH, F, CCH, CN, and NC) has been predicted and characterized. Their geometries (C∞v) with all real harmonic vibrational frequencies were obtained using the second-order Moller–Plesset perturbation theory (MP2) with 6-311++G(d,p) basis set. For each HMgH⋯LiX complex, a lithium bond is formed between the negatively charged H atom of an HMgH molecule and the positively charged Li atom of an LiX molecule. Due to the formation of the complexes, the Mg–H and Li–H bonds are elongated. Interestingly, the Li–X harmonic vibrational stretching frequency is blueshifted in the HMgH⋯LiX (Y = CCH, CN, and NC) complexes and redshifted in the HMgH⋯LiX (X = H, OH, and F) complexes. The binding energy of this type of lithium bond ranges from 12.18 to 15.96 kcal mol−1, depending on the chemical environment of the lithium. The nature of lithium–hydride lithium bond has also been analyzed with natural bond orbital (NBO) and atoms in molecules (AIM).
TL;DR: A tetrel-hydride interaction was predicted and characterized in the complexes of XH3F···HM at the MP2/aug-cc-pVTZ level and NBO analyses demonstrate that both BD(H-M) → BD*(X-F) and BD-M → BD-H) orbital interactions play the stabilizing role in the formation of the complex.
Abstract: 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 BDH–M → BD*X–F and BDH–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 contr...
TL;DR: The hydrogen bond interaction and σ-hole and π-hole bonds are steered by the same mechanisms and the increase of the polarization of bonds to this centre seems to be the common effect.
Abstract: The hydrogen bond interaction and σ-hole and π-hole bonds are steered by the same mechanisms. There is electron charge transfer from the Lewis base to the Lewis acid unit, and further, for various interactions the same mechanisms try to protect the former electronic structure of the Lewis acid centre. The increase of the polarization of bonds to this centre seems to be the common effect. In the case of the A-HB hydrogen bond it is the increase of the polarization of the A-H bond connected with the outflow of the electron charge from the H-atom to the A-centre. For other interactions the outflow of electron charge from the Lewis acid centre is also observed. These electron charge shifts try to protect the doublet/octet structure of the acidic centre. The extremely strong interaction is often equivalent to the formation of new covalent bonds or it may lead to chemical reactions. Numerous interactions may be treated as the preliminary stages of chemical reactions: hydrogen bond - proton transfer, dihydrogen bond - molecular hydrogen release, tetrel bond - SN2 reaction, etc.
TL;DR: By comparison with some related systems, it is concluded that the pnicogen-hydride interactions are stronger than dihydrogen bonds and lithium-Hydride interactions.
Abstract: 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 A, 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.
TL;DR: The results show that the electrostatic interaction plays an important role in the enhancement of halogen bond.
Abstract: Quantum chemical calculations have been performed to study the complex of MCN-LiCN-XCCH (M = H, Li, and Na; X = Cl, Br, and I). The aim is to study the cooperative effect between halogen bond and lithium bond. The alkali metal has an enhancing effect on the lithium bond, making it increased by 77 and 94% for the Li and Na, respectively. There is the cooperativity between the lithium bond and halogen bond. The former has a larger enhancing effect on the latter, being in a range of 11.7–29.4%. The effect of cooperativity on the halogen bond is dependent on the type of metal and halogen atoms. The enhancing mechanism has been analyzed in views with the orbital interaction, charge transfer, dipole moment, polarizability, atom charges, and electrostatic potentials. The results show that the electrostatic interaction plays an important role in the enhancement of halogen bond. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011
TL;DR: In this article, the authors investigated the cooperativity between the S···N(C) bond and the hydrogen/lithium/halogen bond interactions in O2S···NCX·NCH and O2s···CNX···CNH triads (X=H, Li, Cl, and Br).
Abstract: Ab initio calculations were performed to investigate the cooperativity between the S···N(C) bond and the hydrogen/lithium/halogen bond interactions in O2S···NCX···NCH and O2S···CNX···CNH triads (X=H, Li, Cl, and Br). To understand the properties of the systems better, the corresponding dyads are also studied. It is evident that the lithium bond has a bigger influence on the chalcogen bond than vice versa. The results indicate that the enhanced interaction energies of the S···N(C) and X···N(C) interactions in the triad increase in the order NCCl < NCBr < NCH < NCLi and CNCl < CNBr < CNH < CNLi. This is the order of the increasing positive electrostatic potential V S,max on the X atom. The nature of S···N(C) and X···N(C) interactions of the complexes is unveiled by energy decomposition analysis and natural bond orbital (NBO) theory. The cooperativity between both types of interaction is chiefly caused by the electrostatic effects.
TL;DR: In this paper, a direct difference method for the computation of molecular interactions has been based on a bivariational transcorrelated treatment, together with special methods for the balancing of other errors.
Abstract: A new direct difference method for the computation of molecular interactions has been based on a bivariational transcorrelated treatment, together with special methods for the balancing of other errors. It appears that these new features can give a strong reduction in the error of the interaction energy, and they seem to be particularly suitable for computations in the important region near the minimum energy. It has been generally accepted that this problem is dominated by unresolved difficulties and the relation of the new methods to these apparent difficulties is analysed here.
TL;DR: In this paper, a set of criteria are proposed based on the theory of "atoms in molecules" to establish hydrogen bonding, even for multiple interactions involving C-H-O hydrogen bonds.
Abstract: It is shown that the total charge density is a valid source to confirm hydrogen bonding without invoking a reference charge density. A set of criteria are proposed based on the theory of “atoms in molecules” to establish hydrogen bonding, even for multiple interactions involving C-H-O hydrogen bonds. These criteria are applied to several van der Waals complexes. Finally a bifurcated intramolecular C-H-O hydrogen bond is predicted in the anti-AIDS drug AZT, which may highlight a crucial feature of the biological activity of a whole class of anti-AIDS drugs. Almost all the methods of physical chemistry, spectroscopy, and diffraction can be used to recognize and study hydrogen bonding.] Each technique focuses on specific properties in order to detect and characterize this phenomenon in its own way. This work is concerned with the manifestation of hydrogen bonding in the charge density obtained from ab initio calculations. Whereas crystallographers have concluded upon hydrogen bonding via purely geometrical criteria, recent deformation density2 studies allow one to observe hydrogen bonding beyond mere ge~metry.~ However, it is not necessary to subtract an arbitrary (promolecular) charge density from the total density to reveal hydrogen bonding, not even in the interpretation of X-ray experiment^.^ Boyd and Choi have shown in two important contribution^^^^ that the theory of “atoms in molecules’’ (AIM)7,8 can be used to characterize hydrogen bonding solely from the (total) charge density for a large set of acceptor molecules, involving HF and HC1 as donors. In a next stage Carroll and Bader performed a more extended analysis on a large set of BASE-HF comple~es.~ This theory has not only provided new insights in conventional intermolecular hydrogenI0.’ ] bonding but has also been successful in intramolecularI33l4 and x-type hydrogen bonds.I5 Drawing from earlier ob~ervations~~~~ ~.’~~~~ and the present work, we formulate eight concerted effects occurring in the charge density which are indicative of hydrogen bonding. All of these effects can be viewed as necessary criteria to conclude that hydrogen bonding is present. By observation one of these conditions has proven to be sufficient as well. This case study on C-H-O interactions shows that this less common type of hydrogen bonding obeys all of the proposed criteria. Moreover, the multiple interactions appearing in the present five examples do not impair the consistency of the global phenomenon of hydrogen bonding as it expresses itself in the charge density. In spite of an early affirmative infrared review,I6 the old controversy on whether C-H-O hydrogen bonds really exist continued for another decade,” but now the dust has settled’* (for an entertaining account of this controversy, see ref 19). The importance of these bonds has been recognized in crystal engineering’9,20 since C-H-O contacts have a determining influence on packing motifs.21
TL;DR: In this article, the authors applied a set of criteria developed in the context of the theory of atoms in molecules to study dihydrogen bonds, which were previously successfully used to study conventional hydrogen bonds.
Abstract: A new type of hydrogen bond, called a dihydrogen bond, has recently been introduced. In this bond a hydrogen is donated to another (hydridic) hydrogen. We apply a set of criteria developed in the context of the theory of “atoms in molecules” that were previously successfully used to study conventional hydrogen bonds. This method enables one to characterize the dihydrogen bond on the basis of the electron density only. We investigated a dimer structure of BH3NH3 at the ab initio level which contains two dihydrogen bonds that differ in strength. The combination of a theoretical density with our hydrogen-bonding criteria turns out to be a valuable new and independent source of information complementary to techniques such as NMR, IR, and structural crystallography.