Density functional theory cation

Geometries, hyperfme structure, and relative stabilities of the different positional isomers of monodeuterated benzene cations have been studied theoretically by density functional theory, using the B3-LYP functional, and experimentally by ESR and ENDOR spectroscopy. A comparison between theoretical and experimental results at 30 K gives acceptable agreement, but further experiments on multiply deuterated species should improve the analysis by making the effects of deuteration larger. 

D. L. Phillips, W.H. Fang, and X. Zheng, Isodiiodomethane is the methylene transfer agent in cyclopropanation reactions with olefins using ultraviolet photolysis of diiodomethane in solutions a density functional theory investigation of the reactions of isodiiodomethane, iodomethyl radical, and iodomethyl cation with ethylene. J. Am. Chem. Soc. 123(18), 4197-4203 (2001). 

Hertwig, R.H., Hrusak, J., Schroder, D., Koch, W. and Schwarz, H. (1995) The metal-ligand bond strengths in cationic gold(l) complexes. Application of approximate density functional theory. Chemical Physics Letters, 236, 194-200. 

During the last years, more and more researchers have applied density functional theory to small transition-metal complexes and benchmarked the results against either high level wave function based methods or experimental data. A particular set of systems for which reasonably accurate benchmark data are available are the cationic M+-X complexes, where X is H, CH3 or CH2. Let us start our discussion with the cationic hydrides of the 3d transition-metals. 

Ziegler, T., Li, J., 1994, Bond Energies for Cationic Bare Metal Hydrides of the First Transition Series A Challenge to Density Functional Theory , Can. J. Chem., 72, 783. 

Gao, Y., A. L. Focsan et al. (2006). Density functional theory study of the (3-carotene radical cation and depro-tonated radicals. J. Phys. Chem. B 110 24750-24756. 

Potassium cation affinities of several azoles and other compounds in the gas phase were calculated by hybrid density functional theory [B3-LYP with 6-311 + G(3df, 2p) basis set] <2003CEJ3383>. There is a striking difference in binding energies of 177- and 277-1,2,3-triazoles. Some of the collected data are as follows ... 

The results indicate that the formation of long-lived trimethyl substituted silyl cations, in the presence of aromatic solvents, as claimed by Lambert et al.95 is not feasible under these conditions. Persistent silicenium ions require sterically more shielding substituents at silicon or hypercoordinative stabilization.96 98 13C and 29Si NMR chemical shifts were calculated for a series of disilylated arenium ions 85 using density functional theory (DFT). The calculations predict consistently the unsaturated carbon atoms to be too deshielded by 8-15 ppm. Applying an empirical correction, the deviation between experiment and theory was reduced to -0.4 to 9 ppm, and the 13C NMR chemical shift of the highly diagnostic cipso is reproduced by the calculations (Ad = -3.8 to 2.7 ppm).99... 

It is however possible to obtain a physically meaningful representation of 0(r) for cations, in the context of density functional theory. The basic expression here is the fundamental stationary principle of DFT, which relates the electronic chemical potential ju, with the electrostatic potential and the functional derivatives of the kinetic and exchange-correlation contributions [20] ... 

Density functional theory has also been applied successfully to describe the solvent exchange mechanism for aquated Pd(II), Pt(II), and Zn(II) cations (1849 ). Our own work on aquated Zn(II) (19) was stimulated by our interest in the catalytic activity of such metal ions and by the absence of any solvent (water) exchange data for this cation. The optimized transition state structure clearly demonstrated the dissociative nature of the process in no way could a seventh water molecule be forced to enter the coordination sphere without the simultaneous dissociation of one of the six coordinated water molecules. More... 

The W-acyliminium ion can be characterized by FTIR spectroscopy as well.9 The starting carbamate 1 exhibited an absorption at 1694 cm 1 due to the carbonyl stretching, while the V-acyliminium ion 2 generated by the cation pool method exhibited an absorption at 1814 cm 1. The higher wave number observed for the cation is consistent with the existence of a positive charge at the nitrogen atom adjacent to the carbonyl carbon. The shift to higher wave number is also supported by DFT (density functional theory) calculations. 

Oxoiron(V) porphyrins—red in color—an isoelectronic form of oxoiron(IV) porphyrin cation radicals—green—have been proposed (references 55a-c), although the density functional theory calculations have indicated that there are no true oxoiron(V) porphyrins (references 55d-f). Further spectroscopic studies are necessary to confirm the existence of this intermediate. 

In 1997, Jemmis, Schleyer and coworkers studied the structure and energetics of lithi-ated cyclopropenyl cation and their acyclic isomers using ab initio MO (HF/6-31G ) and density functional theory (DFT, B3LYP/6-31G ) methods . Successive lithiation results in... 

Adsorption of cyanide anions can be affected by adsorption of cations. In the solutions containing nonspecifically adsorbed anions, the nature of alkali metal cations was found to influence the measured value of the electrode capacitance at potentials more negative than —0.6 V (versus standard hydrogen electrode (SHE)). At < —l.OV adsorption of CN ions was enhanced in the presence of Li+ and Na+ cations, and inhibited in the presence of Cs+ ions [81]. A combined SERS and density-functional theory has been applied to study cyanide adsorption at Au electrode [82]. The authors have arrived at the conclusion that the polarity of Au—CN bonds falls between that of Au—Cl and Au—Br surface bonds. The binding strength for three different gold surfaces decreased in the order ... 

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