Density functionals reactivity

M. Duran, A. Toro-Labbe, M. Sola, Relations Among Several Nuclear and Electronic Density Functional Reactivity Indices, J. Chem. Phys., 2003, 119,9393-9400. 

Finally, worth specifying that the presented line of systematic formulations of the density functional reactivity indices can be in principle continued when also the expansions containing higher order terms in potential are considered through the nonlinear electronic responses (Senet, 1996, 1997). The recent effects as the spin-philicity and spin-donicity in spin-catalysis phenomena can be rationalized on such generalized analysis (Perez et al., 2002). Therefore, this way, also a closely diagrammatical theory of the absolute /, //, IP, and EA can be built up with increasing accuracy in the non-local effects that the softness kernel approximation may induce. 

Proton affinity and protonation sites of aniline. Energetic behavior and density functional reactivity indices ... 

We will start with the presentation of the Fukui function in the framework of the Density Functional Reactivity Theory and its chemical interpretation, [8-14] followed by a brief account of the different ways to analyze it and ending with its topological analysis. Finally, several applications of this analysis will be shown, and some open problems will be discussed. 

Structure, Magnetic Properties and Reactivity of Open-Shell Species from Density Functional and Self-Consistent Hybrid Methods Vincenzo Barone... 

There have, however, been attempts to correlate Q-e values and hence reactivity ratios to, for example, c NMR chemical shifts 50 or the results of MO calculations 51153 and to provide a better theoretical basis for the parameters. Most recently, Zhan and Dixon153 applied density functional theory to demonstrate that Q values could be correlated to calculated values of the relative free energy for the radical monomer reaction (PA + Mn — PA ). The e values were correlated to values of the electronegativities of monomer and radical. 

Fischer-type carbene complexes, generally characterized by the formula (CO)5M=C(X)R (M=Cr, Mo, W X=7r-donor substitutent, R=alkyl, aryl or unsaturated alkenyl and alkynyl), have been known now for about 40 years. They have been widely used in synthetic reactions [37,51-58] and show a very good reactivity especially in cycloaddition reactions [59-64]. As described above, Fischer-type carbene complexes are characterized by a formal metal-carbon double bond to a low-valent transition metal which is usually stabilized by 7r-acceptor substituents such as CO, PPh3 or Cp. The electronic structure of the metal-carbene bond is of great interest because it determines the reactivity of the complex [65-68]. Several theoretical studies have addressed this problem by means of semiempirical [69-73], Hartree-Fock (HF) [74-79] and post-HF [80-83] calculations and lately also by density functional theory (DFT) calculations [67, 84-94]. Often these studies also compared Fischer-type and... 

The authors carried out theoretical calculations on this system as well as on the [ (PMej) ] system to compare their reactivity with hexafluorobenzene. They found that the barrier for [ (liPr) ] is approximately 10 kJ/mol lower in energy than the corresponding barrier for the phosphine-bearing system. This value was in agreement with the different reactivity of both complexes but could not fully explain the large difference in reaction times. Density functional Theory (DFT) calculations also showed that the trans product is more stable than the cis product (total energies are respectively -130.9 and 91.1 kJ/mol), which was in agreement with the experimental values. 

However, even the best experimental technique typically does not provide a detailed mechanistic picture of a chemical reaction. Computational quantum chemical methods such as the ab initio molecular orbital and density functional theory (DFT) " methods allow chemists to obtain a detailed picture of reaction potential energy surfaces and to elucidate important reaction-driving forces. Moreover, these methods can provide valuable kinetic and thermodynamic information (i.e., heats of formation, enthalpies, and free energies) for reactions and species for which reactivity and conditions make experiments difficult, thereby providing a powerful means to complement experimental data. 

Lev, D. A. Grotjahn, D. B. Amouri, H. Reversal of reactivity in diene-complexed o-quinone methide complexes insights and explanations from ab initio density functional theory calculations. Organometallics 2005, 24, 4232 -240. 

In particular, reactions involving transition-metals have attracted a lot of interest recently because of the connection to catalytic and enzymatic processes. Unfortunately, the proper computational description of such reactions is one of the great challenges of today s theoretical chemistry and the question for the general applicability of density functional methods in the field is an area of active research. We chose to provide a single but - as we think - representative example to illustrate the difficulties one has to face in theoretical studies of transition-metal reactivity. 

Barone, V., 1995, Structure, Magnetic Properties and Reactivities of Open-Shell Species from Density Functional and Self-Consistent Hybrid Methods , in Recent Advances in Density Functional Methods, Part I, Chong, D. P. (ed.), World Scientific, Singapore. 

Parr, R. G., and W. Yang. 1984. Density Functional Approach to the Frontier-Electron Theory of Chemical Reactivity. J. Chem. Soc. 106, 4049. 

Ab initio Hartree-Fock and density functional theory (DFT) calculations were performed to study transition geometries in the intramolecular hetero-Diels-Alder cycloaddition reactions of azoalkenes 20 (LJ = CH2, NFI, O) (Equation 1). The order of the reactivities was predicted from frontier orbital energies. DFT calculations of the activation energies at the B3LYP level were in full agreement with the experimental results described in the literature <2001JST(535)165>. 

The reactions used for coupling affinity ligands to nanoparticles or microparticles basically are the same as those used for bioconjugation of molecules or for immobilization of ligands onto surfaces or chromatography supports. However, with particles, size can be a major factor in how a reaction is performed and in its resultant reaction kinetics. Since particle types can vary from the low nanometer diameter to the micron size, there are dramatic differences in how such particles behave in solution and how the density of reactive groups or functional groups affects reactions. 

The identification of unknown chemical compounds isolated in inert gas matrices is nowadays facilitated by comparison of the measured IR spectra with those computed at reliable levels of ab initio or density functional theory (DFT). Furthermore, the observed reactivity of matrix isolated species can in some instances be explained with the help of computed reaction energies and barriers for intramolecular rearrangements. Hence, electronic structure methods developed into a useful tool for the matrix isolation community. In this chapter, we will give an overview of the various theoretical methods and their limitations when employed in carbene chemistry. For a more detailed qualitative description of the merits and drawbacks of commonly used electronic structure methods, especially for open-shell systems, the reader is referred to the introductory guide of Bally and Borden.29... 

Quantum mechanical approaches have been successfully used to predict hydrogen abstraction potentials and likely sites of metabolism of drug molecules [78-81]. AMI, Fukui functions, and density functional theory calculations could identify potential sites of metabolism. Activation energies for hydrogen abstraction were calculated by Olsen et al. [81] to be below 80 kj/mol, suggesting most CH groups can be metabolized which particular one depends on steric accessibility and intrinsic reactivities. 

In chapter 2, Profs. Contreras, Perez and Aizman present the density functional (DF) theory in the framework of the reaction field (RF) approach to solvent effects. In spite of the fact that the electrostatic potentials for cations and anions display quite a different functional dependence with the radial variable, they show that it is possible in both cases to build up an unified procedure consistent with the Bom model of ion solvation. The proposed procedure avoids the introduction of arbitrary ionic radii in the calculation of insertion energy. Especially interesting is the introduction of local indices in the solvation energy expression, the effect of the polarizable medium is directly expressed in terms of the natural reactivity indices of DF theory. The paper provides the theoretical basis for the treatment of chemical reactivity in solution. 

Other calculations were aimed at predicting the reactivity of some bicyclic 5-6 systems. For instance, the rare [l,4,2]diazaphospholo[4,5- ]pyridine 22 (Scheme 2) was examined for its reactivity (C=P bond) toward dienes in cycloaddition reactions <2005T10521>. The results of density functional theory (DFT) calculations were in good agreement with the experimentally obtained regioselectivity when using unsymmetrical dienes. 

The preparation and reactions of metal cluster ions containing three or more different elements is an area with a paucity of results. The metal cyanides of Zn, Cd (258), Cu, and Ag (259) have been subjected to a LA-FT-ICR study and the Cu and Ag complex ions reacted with various reagents (2,256). The [M (CN) ]+ and [M (CN) +11 ions of copper, where n = 1-5, were calculated to be linear using the density functional method. The silver ions were assumed to have similar structures. The anions [M (CN) +1 of both copper and silver were unreactive to a variety of donor molecules but the cations M (CN) H + reacted with various donor molecules. In each case, where reactions took place, the maximum number of ligands added to the cation was three and this only occurred for the reactions of ammonia with [Cu2(CN)]+, [Cu3(CN)2]+, [Ag3(CN)2]+, and [ Ag4(CN)3]+. Most of the ions reacted sequentially with two molecules of the donor with the order of reactivity being Cu > Ag and NH3 > H2S > CO. 

---