Theoretical Study of Dihydrogen Bonds between (XH) 2, X= Li, Na, BeH, and MgH, and Weak Hydrogen Bond Donors (HCN, HNC, and HCCH) (original) (raw)
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The Journal of Physical Chemistry A, 2002
The results of an ab initio study of complexes with X-H‚‚‚H-M dihydrogen bonds are presented. The proton donors include HCCH and its derivatives HCCF, HCCCl, and HCCCN; HCN and its derivatives HCNLi + and HCNNa + ; CNH, and H 2 O, and the proton acceptor is LiH. For comparison, selected complexes with NaH as the proton acceptor have also been investigated. The structures, binding energies and harmonic vibrational frequencies of all complexes were obtained at the MP2/aug′-cc-pVTZ level of theory. The most stable complexes with C-H groups as proton donors are the cationic complexes NaNCH + :HLi and LiNCH + : HLi. These complexes exhibit very short H‚‚‚‚H distances and are prototypical of dihydrogen-bonded complexes that may dissociate by eliminating H 2 . The calculated binding energies correlate with the H‚‚‚H distance, the elongation of the C-H donor bond, the amount of charge transfer into the H‚‚‚‚H bonding region, and the charge density at the H‚‚‚H bond critical point. As in conventional hydrogen-bonded complexes, the elongation of the proton donor C-H group correlates with the strength of the interaction, and with the red shift of the C-H stretching frequency. Although changes in the Li-H bond length do not follow a simple pattern, the Li-H stretching frequency is blue-shifted in the complexes.
Organometallics, 1996
+ , and OsH 4 (PR 3 ) 3 ) spanning a large range of H-H values is optimized at the B3LYP computational level, yielding satisfactory agreement with available neutron-diffraction data. The electron density resulting from these theoretical calculations is analyzed afterward within the "atoms in molecules" formalism, resulting in a positive assignment of the complexes W(H 2 )(CO) 3 (PR 3 ) 2 and IrH(H‚‚‚H)Cl 2 (PR 3 ) 2 as dihydrogen complexes and of the complexes [Os(H‚‚‚H)(NH 2 (CH 2 ) 2 NH 2 ) 2 (RCO 2 )] + and OsH 4 -(PR 3 ) 3 as dihydride complexes.
A Molecular Electrostatic Potential Analysis of Hydrogen, Halogen, and Dihydrogen Bonds
Hydrogen, halogen, and dihydrogen bonds in weak, medium and strong regimes (<1 to ∼60 kcal/mol) have been investigated for several intermolecular donor−acceptor (D-A) complexes at ab initio MP4//MP2 method coupled with atoms-in-molecules and molecular electrostatic potential (MESP) approaches. Electron density ρ at bond critical point correlates well with interaction energy (E nb ) for each homogeneous sample of complexes, but its applicability to the entire set of complexes is not satisfactory. Analysis of MESP minimum (V min ) and MESP at the nuclei (V n ) shows that in all D-A complexes, MESP of A becomes more negative and that of D becomes less negative suggesting donation of electrons from D to A leading to electron donor−acceptor (eDA) interaction between A and D. MESP based parameter ΔΔV n measures donor−acceptor strength of the eDA interactions as it shows a good linear correlation with E nb for all D-A complexes (R 2 = 0.976) except the strongly bound bridged structures. The bridged structures are classified as donor−acceptor−donor complexes. MESP provides a clear evidence for hydrogen, halogen, and dihydrogen bond formation and defines them as eDA interactions in which hydrogen acts as electron acceptor in hydrogen and dihydrogen bonds while halogen acts as electron acceptor in halogen bonds. − (electron donors) with different electron acceptors. Throughout this paper, E nb represents the interaction energy calculated at MP4//MP2 method and the standard notations ρ and ∇ 2 ρ are used to indicate the electron density at the bond critical point (bcp) of the electron donor−acceptor bond and the Laplacian of the electron density at the bcp. Figure 7. Change in V min upon bond formation in electron donor−acceptor−donor complexes (a) F − ...IF and (b) F − ...IBr. The black dots represent the location of the most negative MESP-valued point and the corresponding V min values in kcal/mol are also depicted.
Dihydrogen Bonding: Donor–Acceptor Bonding (AH⋅⋅⋅ HX) versus the H2 Molecule (A H2 X)
2009
Abstract: Dihydrogen bonds (DHBs) play a role in, among others, crystal packing, organometallic reaction mechanisms, and potential hydrogen-storage materials. In this work we have analyzed the central HÀH bond in linear H4, LiH··· HX, BH4 À··· HX, and AlH4 À··· HX complexes with various X by using the quantitative molecular orbital model contained in Kohn–Sham density functional theory at the BP86/TZ2P level of theory. First, we address the questions of if and how one can distinguish, in principle, between a
The Journal of chemical …, 2003
The structural, energetic, and spectroscopic properties of the dihydrogen-bonded complexes LiH¯H 2 , LiH¯CH 4 , LiH¯C 2 H 6 , and LiH¯C 2 H 2 are investigated. In particular, the interaction energy is decomposed into physically meaningful contributions, and the calculated vibrational frequencies, the magnetic resonance shielding constants, and inter-and intramolecular spin-spin coupling constants are analyzed in terms of their correlation with the interaction energy. Unlike the other three complexes, which can be classified as weak van der Waals complexes, the LiH¯C 2 H 2 complex resembles a conventional hydrogen-bonded system. The complexation-induced changes in the vibrational frequencies and in the magnetic resonance shielding constants correlate with the interaction energy, as does the reduced coupling 2h J HX between the proton of LiH and hydrogen or carbon nucleus of the proton donor, while 1h J HH do not correlate with the interaction energy. The calculations have been carried out using Møller-Plesset perturbation theory, coupled-cluster theory, and density-functional theory.
Chemical Physics Letters, 2007
Theoretical prediction of the formation of hydrogen-rich complexes of s-block metal ions and dihydrogen molecules, MH 16 , (M = Li 1+ , Na 1+ , K 1+ , Be 2+ , Ca 2+ , and Mg 2+) is reported. The number of hydrogen molecules attached to the metal cation is the highest ever reported in the literature. The interaction between s-block metal ions and hydrogen is found to be weak and the binding energy calculated by MP2 method using cc-pVDZ basis set is observed to be of the order of À30 to À13.5 kcal/mol and À180 to À60 kcal/ mol for alkali and alkaline earth metal cations, respectively. Using this simple ion-molecule interaction, the possibility of the application of these complexes for developing hydrogen storage materials is discussed.
Nature of the chemical bond in complex hydrides, NaAlH4, LiAlH4, LiBH4 and LiNH2
Journal of Alloys and Compounds, 2005
The most stable crystal structures of complex hydrides, MXH n (NaAlH 4 , LiAlH 4 , LiBH 4 and LiNH 2) were simulated by the plane-wave pseudopotential method. The local chemical bonds between constituent ions were simulated using the DV-X␣ molecular orbital method. As a result, it was found that the covalent interaction is operating between X and H ions to form a XH n ion in MXH n. In addition, the ionic interaction is operating between M and XH n ions through the charge transfer from M to XH n ions. On the basis of this understanding of the nature of the chemical bond between ions, a phase stability diagram of complex hydrides was proposed using two parameters. One is the bond energy of XH diatomic molecules and the other is electronegativity difference, Φ X M , between M and X ions. The calculated stability change by doping into NaAlH 4 could by explained qualitatively following this diagram. This diagram will provide us a clue to the modification of hydrides to lower the hydrogen decomposition temperature.
Journal of The American Chemical Society, 1975
Hydrogen-bonded dimers involving first-and second-row hydrides have been studied theoretically with ab initio molecular orbital methods, using a 431G basis set. Certain generalizations about H-bonded dimers found in a previous stu-dyZa of first-row dimers (those involving "3, H20, and HF) are supported by this study; others require modification. In addition to studying the dependence of H-bond energy and properties on the row of the periodic table, we examine the dependence of H-bond energies on the "hybridization" of the electron donor, including HCN, H2C0, H2CS, HNC, and HCP as electron donors. We have also studied ionic H bonds, ''P" H bonds, and H-bonded trimers in an attempt to relate their properties to those of the more conventional H-bonded dimers. Can a C-H bond be an effective H-bond proton donor? We attempt to answer this question by examining the proton donor ability of CH4 and CHF3. Electrostatic potentials turn out to facilitate our understanding of H-bond energies and structures, being more useful than Mulliken populations in rationalizing H-bond energies. Finally we address ourselves to the question of predicting dimer H-bond energies from the monomers involved. Using a very simple algebraic model, we are able to predict the H-bond energy of a total 144 H-bonded complexes, using as a basis our theorctical calculations on 25 complexes.
Comparison between hydrogen and dihydrogen bonds among H3BNH3, H2BNH2, and NH3
The Journal of Chemical Physics, 2003
Several possible binary complexes among ammonia-borane, aminoborane, and ammonia, via hydrogen and/or dihydrogen bonds, have been investigated to understand the effect of different hybridization. Møller-Plesset second-order perturbation theory with aug-cc-pVDZ basis set was used. The interaction energy is corrected for basis set superposition error, and the Morokuma-Kitaura method was employed to decompose the total interaction energy. Like H 3 BNH 3 , the sp 2 hybridized H 2 BNH 2 also participates in Hand dihydrogen bond formation. However, such bonds are weaker than their sp 3 analogs. The contractions of BN bonds are associated with blueshift in vibrational frequency and stretches of BH and NH bonds with redshift. The polarization, charge transfer, correlation, and higher-order energy components are larger in dihydrogen bonded complexes, compared to classical H-bonded ammonia dimers.