Radicals density functional theory calculations

Figure 7.20. Top ORTEP representation from the X-ray structure of the localized radical 45, and selected bond parameters (the parenthesis show the values determined computationally at the UB3LYP/6-31G level of theory). Bottom Density functional theory calculations for the rotation of the tert-butyl group. (Taken from ref. 113.)...

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. 

The 1,2-hydrogen shift isomers of neutral (singlet and triplet) thiazole and its radical cation have been investigated87 by a combination of mass spectrometric experiments and hybrid density functional theory calculations. An unexpected isomerization of A-aryl-3-amino-4-nitroisothiazole-5(2//)-imines (71) to 2-(benzothiazol-2-yl)-2-nitro-ethene-1,1-diamines (72) has been reported.88... 

Baker, J. M. Dolbier, W. R. Density functional theory calculations of the effect of fluorine substitution on the cyclobutylcarbinyl to 4-pentenyl radical rearrangement. J. Org. 

Recent Developments in Configuration Interaction and Density Functional Theory Calculations of Radical Hyperfine Structure. 

A similar cycloreversion in 1,2-dithiolan cation-radical was used to prepare CH2S2 ions which were reduced with Xe to generate elusive CH2S2 molecules. The structure of neutral CH2S2, dithiirane or CH2=S=S, was not determined from the +NR+ mass spectra [158]. Density functional theory calculations favored both dithiirane and its cation-radical as being more stable than CH2=S=S and CH2=S=S+, respectively, and so the authors tentatively assigned cyclic structure to the ion and neutral. 

The 8-endo cyclization of /V-(4-pcntyl) iodoacetamides was investigated by density functional theory calculations at the B3LYP/6-31G level (Scheme 2 <2005JOC1539>) (see also Section 12.8.5.3). The calculations revealed the propensity of iV-alkenyl-substituted ct-carbamoyl radicals for 8-endo cyclization of both s-cis and s-trans conformational transition stmctures, while 1-exo transition stmctures were less stable, although both of comparable energy. Theoretical assessments are in agreement with experimental findings. 

The SOF4 anion has been generated by y-irradiation of CsSOF5 and characterized by its isotropic EPR spectrum at 27°C [153]. The SOF4 anion has a /vew o-octahedral structure of C4v symmetry in which the equatorial positions are occupied by four equivalent fluorines, one axial position is occupied by a doubly bonded oxygen and the second axial position by the sterically active free valence electron. The structure and spin density of SOF4 have been analyzed by local density functional theory calculations and the isoelectronic POF42 radical anion has also been calculated. 

Are Nl and N2 really through-space delocalized radical anions as illustrated in Fig. 7.12 A rather clear indication can be derived from the conspicuously large H hfc values of the y protons in NT and N2 of 0.625 and 0.842mT. This size can only be rationalized by a dominating electron density between the formaUy nonbonded diazene units and is in perfect agreement with density functional theory calculations. 

A recent study employing ESR spectroscopy and density functional theory calculations has shown that the adenine cation radical (A +) in aqueous glassy solutions of dAdo and of the DNA oligomer (dA) is stabilized by base stacking interactions. The pK of the adenine cation radical in isolated dAdo in aqueous solutions is ca. 1 and, therefore, A " readily deprotonates from its exocylic amine group, nevertheless, these researchers find that the pK of the adenine cation radical in stacked systems to be ca. 8 at 150 K. It appears that the hole delocalizes over several bases, which stabilize it by charge resonance interactions. Calculations show that in the... 

The density functional theory calculations mentioned earlier also modeled the ring-opening of cyclobutane radical cation [87]. This reaction proceeded via a distorted trapezoid transition state with two shorter (142.2, 147.1 pm) and two longer bonds (187.7, 208.4 pm), forming the "anti -complex (one long bond 221.6 pm), similar to that calculated earlier [168]. 

Tian, F., Bartberger, M. D., Dolbier, W. R., Jr. Density Functional Theory Calculations of the Effect of Fluorine Substitution on the Kinetics of Cyclopropylcarbinyl Radical Ring Openings. J. Org. Chem. 1999, 64, 540-546. 

In what follows, we propose a phenomenological model of the chemisorbed radical-anion standing in the electrochemical double-layer. We shall hence detail the reasons why this chemisorbed radical anion is intrinsically unstable but most probably has a finite lifetime on the polarized metallic surface. We outline the procedure through which we expect that an order of magnitude of the lifetime of the chemisorbed radical-anion may be evaluated numerically via this model. The model potential felt by the radical-anion as it is formed on the polarized electrode is described as the sum of three terms, for which a parametrisation is proposed. One of these terms is meant to include both the surrounding solvent and the repulsion by the polarized electrode, thanks to a mean, locally uniform, electric field. In the present paper, the intensity of this uniform electric field is calibrated on the basis of a conparison between experimental Stark-Tuning shifts for CO chemisorbed on palladium surfaces in solution and Density Functional Theory calculations of field-induced vibrational shifts for CO chemisorbed on palladium clusters. The shape of the resulting model potential is then discussed. 

In the mechanism put forth by Siegbahn/" " depicted in Figure 26, successive S-state advancements via PCET path B leads to the formation of a /i-oxyl radical. The mechanism is based largely upon density functional theory calculations. The role of Ca is to polarize the Mn—O bonds and direct the placement of the radical. The O—O bond-forming step is as yet unclear in the density functional theory (DFT) calculations, but it appears to involve reaction of the oxyl radical with outer-sphere H2O to form a hydroperoxide species that is oxidized to O2. 

Our approach starts with and extends a mechanism initially proposed by Carpenter [175] who reported a computational study showing several very important new reaction pathways for the reaction of vinyl and phenyl radicals with molecular oxygen using semi-empirical calculations. Mebel et al. [33] extended the work of Carpenter on vinyl with Density Functional Theory calculations, B3LYP/6-311g(d,p), for structures and energies as well as G2M calculations to verify the energetics. 

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