Density Functional Study of H−D Coupling Constants in Heavy Metal Dihydrogen and Dihydride Complexes: The Role of Geometry, Spin−Orbit Coupling, and Gradient Corrections in the Exchange-Correlation Kernel (original) (raw)
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The Journal of Physical Chemistry A, 2002
In our continuing effort to identify NMR spin-spin coupling constants as fingerprints for hydrogen bond type and use these to obtain structural information, EOM-CCSD calculations have been performed to determine one-bond ( 1d J H-H ) and three-bond ( 3d J X-M ) spin-spin coupling constants across X-H‚‚‚H-M dihydrogen bonds for complexes with 13 C-1 H, 15 N-1 H, and 17 O-1 H proton-donor groups and proton-acceptor metal hydrides 7 Li-1 H and 23 Na-1 H. Unlike two-bond spin-spin coupling constants across N-H-N, N-H-O, O-H-O, and Cl-H-N hydrogen bonds that are determined solely by the Fermi-contact term, 1d J H-H receives nonnegligible contributions from the paramagnetic spin-orbit and diamagnetic spin-orbit terms. However, these terms tend to cancel, so that the curve for the distance dependence of 1d J H-H is determined by the distance dependence of the Fermi-contact term. The value of 1d J H-H is dependent on the nature of the proton donor and proton acceptor, and the relative orientation of the bonded pair. Hence, it would be difficult to extract structural information from experimentally measured coupling constants unless EOM-CCSD calculations were performed on a model complex that closely resembles the experimental complex. 3d J C-Li values for the equilibrium structures of seven linear complexes stabilized by C-H‚‚‚H-Li bonds are dependent on C-Li distances, and are also sensitive to structural changes which remove any one of these four atoms from the dihydrogen bond. 3d J O-M for the complexes HOH:HLi and HOH:HNa exhibit unusual behavior as a function of the O-M distance, increasing with increasing distance through a change of sign, reaching a maximum, and then subsequently decreasing. and qzp on nonhydrogen atoms except for Li and Na. This basis set is not available for these atoms, so the corresponding triplesplit basis sets were used. Hydrogen atoms not involved in the dihydrogen bond have been described by the Dunning cc-pVDZ basis. 23-25 Coupling constants have been computed for each equilibrium structure, and for the optimized linear structures of CNH:HLi and CNH:HNa. In addition, the dependence of the total coupling constant and the PSO, DSO, FC, and SD terms on the H‚‚‚H distance and the orientation of the proton donor and proton acceptor have been investigated. Spin-spin coupling constants were computed using the ACES II program. 26 All calculations were carried out on the Cray SV1 computer at the Ohio Supercomputer Center.
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.
Wave Function and Density Functional Theory Studies of Dihydrogen Complexes
Journal of Chemical Theory and Computation, 2014
We performed a benchmark study on a series of dihydrogen bond complexes and constructed a set of reference bond distances and interaction energies. The test set was employed to assess the performance of several wave function correlated and density functional theory methods. We found that second-order correlation methods describe relatively well the dihydrogen complexes. However, for high accuracy inclusion of triple contributions is important. On the other hand, none of the considered density functional methods can simultaneously yield accurate bond lengths and interaction energies. However, we found that improved results can be obtained by the inclusion of nonlocal exchange contributions.
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.
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.
A density functional study of weakly bound hydrogen bonded complexes
Chemical physics, 1998
. Ž . Density functional theory DFT calculations with B3LYP exchange-correlation functional and using 6-31 qqG d,p Ž . basis functions have been performed on weakly bound hydrogen bonded complexes between HX X s F,Cl and alkenes and Ž . alkynes, such as C H , C HX X s H,F,Cl , C H and allene. Calculations have also been carried out at MP2 s full level 2 4 2 4 2 of theory and using the same basis set as mentioned above for comparison with the DFT results. It has been observed that the BSSE uncorrected binding energies obtained from the B3LYP calculations are always lower than the corresponding MP2 results whereas opposite trend has been observed after BSSE correction. Hydrogen bond lengths obtained from MP2 and B3LYP calculations differ insignificantly. The H-X frequency shift due to complex formation has been well reproduced by the B3LYP method. q 1998 Elsevier Science B.V. All rights reserved. 0301-0104r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 3 0 1 -0 1 0 4 9 8 0 0 1 1 1 -6
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.
Two-Bond 15N−19F Spin−Spin Coupling Constants (2hJN-F) across N−H+...F Hydrogen Bonds
Journal of Physical Chemistry A, 2003
Two-bond 15 N-19 F NMR spin-spin coupling constants (2h J N-F) have been computed using equation-ofmotion coupled cluster singles and doubles theory (EOM-CCSD) for a variety of cationic complexes stabilized by traditional N-H + ‚‚‚F hydrogen bonds. The proton donors include protonated sp bases derived from HCN, protonated sp 2 aromatic rings and imines, and protonated sp 3 bases derived from NH 3 , with FH as the proton acceptor. 2h J N-F is determined solely by the Fermi-contact term, which is distance dependent. The absolute values of N-F coupling constants for cationic complexes are significantly greater than the F-N coupling constants for neutral complexes stabilized by traditional F-H‚‚‚N hydrogen bonds over a range of N-F distances. This may be attributed to the greater proton-shared character of hydrogen bonds in cationic complexes. Moreover, at a given distance, values of 2h J N-F for complexes with sp and sp 2 nitrogens as proton donors are considerably greater than 2h J N-F values for complexes with sp 3 nitrogens as donors. When the cationic complexes are grouped according to the hybridization of the nitrogen, good correlations are found between 2h J N-F and the N-F distance. Small perturbations of the N-H + ‚‚‚F hydrogen bond from linearity are associated with only small decreases in 2h J N-F .
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.
Journal of Molecular Structure: THEOCHEM, 1998
The study of a large variety of hydrogen-bonded complexes (protic, hydric and protic-hydric) leads to the conclusion that the electron density at the bond critical point (r BCP) is an additive property when it is expressed relatively (dimensionless). Equation [r BCP (01)/r BCP (1)] 1 [r BCP (02)/r BCP (2)] 1 represents the additive property for the protic cases, for the hydric cases the sum being equal to 2. The isolated molecules can be used to estimate r BCP (01) and r BC p(02) provided a scaling factor of 0.98 is used.