Quantum-chemical calculations radical cation

The Hamiltonian provides a suitable analytic form that can be fitted to the adiabatic surfaces obtained from quantum chemical calculations. As a simple example we take the butatriene molecule. In its neutral ground state it is a planar molecule with D2/1 symmetry. The lowest two states of the radical cation, responsible for the first two bands in the photoelectron spectrum, are and... 

In this paper the electtode anodic reactions of a number of dihydropyridine (DHP) derivatives, quantum-chemical calculations of reactions between DHP cation-radicals and electrochemiluminescers anion-radicals (aromatic compounds) and DHP indirect ECL assay were investigated. The actuality of this work and its analytical value follow from the fact that objects of investigation - DHP derivatives - have pronounced importance due to its phaiTnacology properties as high effective hypertensive medical product. 

Figure 7. The PES of the X2B2S and A -Bi, states of the butatriene radical cation, (a) Diabatic surfaces, (b) Adiabatic surfaces. The surfaces are obtained as eigenfucations of the vibronic coupling model Hamiltonain that fitted to reproduce quantum chemical calculations. The coordinates are shown in Figure lc. See Section III. D for further details.

Localization or delocalization of an excess electron (in anion radicals) and a hole (in cation radicals) along the polymer chain determines the electronic conductivity of the polymeric ion radicals. From this point of view, the cation radical of vinylene-bridged-oc-tithiophene oligomer should be mentioned. Quantum chemical calculation (Casado et al. 2000) indicates that the hole localizes in the middle of the molecule. The hole extends over the central part built from four thyenylene units. 

As a result of quantum chemical calculations on the oz Z/zo-dinitrobenzenc anion radical (Todres 1990), the attack of cation-type electrophiles is predicted to take place at the two para positions of the benzene ring, ortho Substitutions seem to be impossible. The experiments have confirmed this theoretical prediction. 

Belevskii, V.N., Tyurin, D.A., Chuvylkin, N.D. 1998. Reactivity of radical cations in the radiolysis of amides. An ESR study and quantum chemical calculation. High Energy Chem. 32(5) 305-315. (Translated from Khimiya Vysokikh Energii 32(5) 342-352.)... 

In Equation 6.38, the heat of formation terms, AHf (X) and AHf (X+), refer to the neutral species, X, and the associated radical cation, X+, in their respective ground states they would both usually require separate quantum chemical calculations, including geometry optimizations. 

For pagodane-related carbon skeletons 4C/3e radical cations with tight and extended geometries could be established by spectroscopy (predominately EPR) and quantum chemical calculations at the DFT level of theory. Such structures resemble frozen stages of cycloadditions/cycloreversions on the hyper energy surface of the hole-catalyzed cyclobutane formation. 

The transient observed in neutral solution containing MME by optical absorption with = 380 nm was assigned to a monomeric radical cation characterized by a three-electron-bond between sulfur and nitrogen atoms in a five-membered ring configuration and confirmed by quantum chemical calculations (Chart 6). 

The radical cation formed upon ionization of ANI has been studied by different spectrometric techniques, including photoelectron, two-color photoionization, ZEKE70,80,199,212-226 and mass107,227-232 spectrometries. In most cases, the technique used has been coupled with infrared spectroscopy, which allowed the fine vibrational spectrum of the ion to be determined, in both line position and intensity. For example, the ZEKE photoelectron spectrum216 was recorded by exciting to the neutral S ( 52) excited state, and well-resolved vibrational bands of the cation were observed. In conjunction with quantum chemical calculations of fundamental frequencies, an assignment of the observed vibrational bands can thus be made. A few theoretical studies56,107,218,233,234 have also been devoted to the radical cation. 

The quantity of radical cations formed by dissociation of is dependent on the polarity of the solvent with less polar solvents such as SO2 or SO2CIF favoring the formation of radical (mono-)cations if compared to polar solvents Hke HE or oleum. This can be understood by quantum chemical calculations with inclusion of solvation energies that approximate solvents of different polarities. A measure for the polarity of a solvent is the dielectric constant (DC) and a graphic representation of the calculated Gibbs energies of selected dissociation equilibria of in solvents with dielectric constants between 1 and 30 is given in Fig. 6 [3]. For comparison the DC of SO2 at 298 K is 14 and that of HF is 83. 

We recall that ethyl cation has a bridged, nonclassical structure, and that the classical CH3CH2+ is calculated by high level quantum chemical calculations (36) to be ca. 6 kcal mol 1 less stable. Combining this difference with the experimentally measured heats of formation of ethyl cation and of the neutral ethyl radical, we derive the "classical" ionization potential of CH3CH2 to be 8.4 eV = 193 kcal mol"1. Consider now the geminally-fluorinated ethyl radicals CH3CF2 ,... 

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