Valence anion

DEBYE-HOCKEL LIMITING LAW. The departure from ideal behavior in a given solvent is governed by the ionic strength of the medium and the valences of the ions of the electrolyte, but is independent of their chemical nature. For dilute solutions, the logarithm of the mean activity is proportional to the product of the cation valence, anion valence, and square root of ionic strength giving the equation... 

Electron transmission spectroscopy results bB3LYP/D95V+(D) except for G which is estimated from trends CDFT (B3LYP/6-311+G(2df,p)) destimated from stable valence anion complexes, e.g.., U(Ar)- ebest estimates from DFT basis set dependence study (vide infra). Thymine from ref. [88], note these values are likely too positive by 0.15 eV fEstimate of keto tautomer from enol tautomer experimental value (—0.46eV) plus calculated difference in energy between keto and enol tautomers (0.28 eV) ref. [94],... 

STABLE VALENCE ANIONS OF NUCLEIC ACID BASES AND DNA STRAND BREAKS INDUCED BY LOW ENERGY ELECTRONS... 

The bottleneck of very short lifetimes of resonace states (10 14s) becomes less severe once one assumes that the primary role of resonance states is to provide doorways to bound valence anionic states, with lifetimes determined by kinetics of the following chemical reactions [36], The reactions might proceed on these regions of potential energy surfaces, at which valence anions are bound with respect to the neutral species. The rates of these chemical transformations, e.g., the SSB formation, do not have to compete with short lifetimes of resonance states. It is worth noting that even for a kinetic barrier of ca. 20 kcal/mol, the half lifetime amounts (at 298 K) to about 30 seconds. Hence, if the kinetic barrier for SSB formation were lower than 20-23 kcal/mol, all nucleotides that could form stable anions would have enough time to cleave the C-O bond on the timescale of the electrophoretic assay of DNA damage. 

A markedly different proposal for the DNA cleavage mechanism (from that reported by Leszczynski s) group was published by us in 2005 [36], To the best of our knowledge this was the first mechanism presented in the literature for single strand break formation to be based on the formation of stable valence anions of nucle-obases. Figure 21-29 displays the main idea of our suggestion for the C3 -0 bond scission in 3 -phosphate of cytidine. 

Mazurkiewicz K, Haranczyk M, Gutowski M, Rak J, Radisic D, Eustis SN, Wang D, Bowen KH (2007). Valence anions in complexes of adenine and 9-methyladenine with formic acid Stabilization by intermolecular proton transfer. J Am Chem Soc 129 1216-1224. 

Then, the forces acting on a z,-valence cation and a z2-valence anion become ... 

Of equal historical significance are the contributions of the groups of John Brauman (Stanford) and Carl Lineberger (Colorado). A number of free-radicals are known to exhibit both dipole-bound and more tightly bound conventional (valence) anions. The groups of Brauman and Lineberger have reported very narrow resonance features in the photodetachment spectrum corresponding to rotationally excited shape and Feshbach resonances for many of these dipole-bound radical anions. 

RET peak around = 20 is attributed to interaction of the quadrupole-bound state with the known valence anion state at —0.9 eV. ... 

The signature for creation of valence anions ( free electron attachment), on the other hand, is the observation of a smooth variation of the RET -dependencies over a wide range of n corresponding to high w-values. 

Nitrobenzene, j zra-dinitrobenzene (/zDNB) and me/a-dinitrobenzene (mDNB) anions have both diffuse multipole-bound and valence-anion states. For nitrobenzene and m-dinitrobenzene, the diffuse states are believed to correspond to dipole-bound anions whereas />DNB anions are considered to be primarily described as quadrupole-bound states. Nitrobenzene anions (NB ) in both valence and dipole-bound states were examined using RET spectroscopy. R<3ra-dinitrobenzene (zero dipole moment and a large quadrupole moment) and me <3-dinitrobenzene (large dipole moment and a small quadrupole moment) were also studied using R T 106 20 shows the /-dependence of the reaction rates for... 

Meta-dinitrobenzene has a large dipole moment (p = 4.29 D), very close to that of nitrobenzene, and a quadrupole moment of Q = - -18 a.u. Its parallel and perpendicular polarizabilities are estimated to be 21.2 and 17 A, respectively. From the electrostatic model, the predicted electron affinity of mDNB is 105 25 meV, corresponding to a peak in the RET curve at around n = 7. The curve for mDNB (not shown) is very different from the RET curve corresponding to pDNB. The broad peak at = 11-12 is not present and is replaced by a very small peak at = 8, close to the predicted value for the dipole-bound mDNB anion. The anions reported here are not observed to undergo field detachment. Again, this observation is attributed to the coupling of these diffuse states with the ground valence anion state. 

Readers who wish to learn more about how molecular EAs (and to a lesser extent, IPs) have been studied theoretically are directed to this author s web site http //simons.hec. utah.edu as well as to a series [38] of his reviews and chapters. The species that this group have examined include dipole-bound anions, zwitterion ions, conventional valence anions, multiply charged anions as well as a wide variety of metastable anions. 

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