Density functional theory , hydrogen

The basis set is 6-31G(d,p), and electron correlation at the MP2 level is included. A similar structure is obtained with the AMI and PM3 semi-empirical methods. Density functional theory at the B3LYP/6-31G(dp,p) level also produced the same structure for this ion-pair. The only observed differences between the semi-empiri-cal and the ab initio structures were slightly shorter hydrogen bonds (PM3 and AMI) between FI, F2, and F5 and the G2-F1 (H18) on the imidazolium ring. 

ROsch N (1999) A Critical Assessment of Density Functional Theory with Regard to Applications in Organometallic Chemistry. 4 109-163 Roucoux A (2005) Stabilized Noble Metal Nanoparticles An Unavoidable Family of Catalysts for Arene Derivative Hydrogenation. 16 261-279... 

Greeley J, Nprskov JK. 2007. Large-scale density functional theory-based screening of alloys for hydrogen evolution. Surf Sci 601 1590. 

Skulason E, Karlberg GS, Rossmeisl J, Bligaard T, Greeley J, Jonsson H, Nprskov JK. 2007. Density functional theory calculations for the hydrogen evolution reaction in an electrochemical double layer on the Pt(lll) electrode. Phys Chem Chem Phys 9 3241-3250. 

Watson GW, Wells RPK, Willock DJ, Hutchings GJ. 2001. A comparison of the adsorption and diffusion of hydrogen on the 111 surfaces of Ni, Pd, and Pt from density functional theory calculations. J Phys Chem B 105 4889-4894. 

Detection of the dA N1 and dC N3 adducts may not in one sense be particularly important for DNA based on their central position within the helical conformation and hydrogen bonding network.37,38 Still, the deoxynucleoside studies helped to focus attention on the reversibility of alkylation by QM and provided insight into the reactions of duplex DNA described below in Section 9.3. Reaction at the deoxynucleoside level also provided an essential system for developing a theoretical treatment of QM reaction.50-52 Computations based on density functional theory well rationalized the published results on d A and correctly anticipated the results on dG and dC reviewed above and described in more detail in Chapter 2 (Freccero). 

This, at first glance innocuous-looking functional FHK[p] is the holy grail of density functional theory. If it were known exactly we would have solved the Schrodinger equation, not approximately, but exactly. And, since it is a universal functional completely independent of the system at hand, it applies equally well to the hydrogen atom as to gigantic molecules such as, say, DNA FHK[p] contains the functional for the kinetic energy T[p] and that for the electron-electron interaction, Eee[p], The explicit form of both these functionals lies unfortunately completely in the dark. However, from the latter we can extract at least the classical Coulomb part J[p], since that is already well known (recall Section 2.3),... 

In reviewing the performance of density functional theory applied to hydrogen bonded complexes of moderate strength, we repeatedly noted a systematic underestimation of the interaction energies for many types of functionals, usually below 2 kcal/mol. This has been related by some researchers to the inability of modem functionals to describe those contributions to intermolecular binding energies which stem from dispersion forces. Dispersion... 

One of the simplest chemical reactions involving a barrier, H2 + H —> [H—H—H] —> II + H2, has been investigated in some detail in a number of publications. The theoretical description of this hydrogen abstraction sequence turns out to be quite involved for post-Hartree-Fock methods and is anything but a trivial task for density functional theory approaches. Table 13-7 shows results reported by Johnson et al., 1994, and Csonka and Johnson, 1998, for computed classical barrier heights (without consideration of zero-point vibrational corrections or tunneling effects) obtained with various methods. The CCSD(T) result of 9.9 kcal/mol is probably very accurate and serves as a reference (the experimental barrier, which of course includes zero-point energy contributions, amounts to 9.7 kcal/mol). 

Bernardi, F., Bottom, 1997, Polar Effect in Hydrogen Abstraction Reactions from Halo-Substituted Methanes by Methyl Radical A Comparison Between Hartree-Fock, Perturbation, and Density Functional Theories , J. Phys. Chem., 101, 1912. 

Guo, H., Sirois, S., Proynov, E. I., Salahub, D. R., 1997, Density Functional Theory and its Applications to Hydrogen-bonded Systems in Theoretical Treatments of Hydrogen Bonding, Hadzi, D. (ed.), Wiley, New York. 

Milet, A., Korona, T., Moszynski, R., Kochanski, E., 1999, Anisotropic Intermolecular Interactions in Van der Waals and Hydrogen-Bonded Complexes What Can we Get from Density Functional Theory , J. Chem. Phys., Ill, 7727. 

Mo, O., Yafiez, M., 1998, Density Functional Theory Calculations on Hydrogen-Bonded Tropolone-(H20)2 Clusters , J. Phys. Chem. A, 102, 8174. 

Nguyen, M. T., Creve, S., Vanquickenborne, L. G., 1996, Difficulties of Density Functional Theory in Investigating Addition Reactions of the Hydrogen Atom , J. Phys. Chem., 100, 18422. 

Topol, I. A., Burt, S. K., Rashin, A. A., 1995, Can Contemporary Density Functional Theory Yield Accurate Thermodynamics for Hydrogen Bonding , Chem. Phys. Lett., 247, 112. 

Density functional theory study of aqueous-phase rate acceleration and endo/exo selectivity of the butadiene and acrolein Diels-Alder reaction72 shows that approximately 50% of the rate acceleration and endo/exo selectivity is attributed to hydrogen bonding and the remainder to bulk-phase effects, including enforced hydrophobic interactions and cosolvent effects. This appears to be supported by the experimental results of Engberts where a pseudothermodynamic analysis of the rate acceleration in water relative to 1-propanol and 1-propanol-water mixtures indicates that hydrogen-bond stabilization of the polarized activated complex and the decrease of the hydrophobic surface area of the reactants during the activation process are the two main causes of the rate enhancement in water.13... 

The crystal structures of raer-[lr(en)(enl I )C13]C1 1120 and mer-[Ir(en)(en )Cl3] show that the coordination geometry of Ir is almost identical in the two complexes, with the only difference being in the conformation of the unidentate en and enH+ groups.122 Density functional theory and ab initio calculations have been performed on the two complexes and the calculated confirmations agree well with the X-ray diffraction values.123 The enH+ ligand is stabilized via intramolecular N—H - - Cl hydrogen bonds. 

However, recently Inderwildi et al.28 showed by density functional theory (DFT) calculations that hydrogenation of CO leading to formyl (oxomethyli-dyne) and subsequent conversion toward CH2 show lower activation barriers than CO dissociation. 

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