Multiply charged anions

We have been able, however, on occasions to use a very simple model to help understand specific plant problems where river water analyses were available and on one occasion to show that at different times the boiler water had (as corrosion evidence suggested) alternated between acidic and alkaline conditions. The model assumes that by 350 C any normally dissociated multi-charged ions will be sufficiently unstable that they will undergo whatever appropriate hydrolysis reactions can reduce their charge to unity. Whether the water goes acid or alkaline then simply depends on whether the total (equivalent) concentration of multiply charged cations exceeds or is smaller than the concentration of multiply charged anions. 

Generally the solubilities of the salts are somewhat lower than the corresponding solubilities in water and somewhat higher than those in most dipolar aprotic solvents. The alkali metal chlorides are considerably less soluble than the perchlorates — the reverse of the trend in water. In general, salts of multiply-charged anions (particularly sulfates and carbonates) tend to be fairly insoluble. 

The primary impetus for preparing each of the oligosapphyrins described above, and indeed all of the three-dimensional sapphyrins, was to obtain systems capable of binding multiply charged anionic species with high specificity and affinity. This was obtained, with remarkable success, in the case of the sapphyrin oligomers. These systems were found to function as remarkably good receptors of dicarboxylate anions, nucleotide di- and triphosphates, and amino acids. ... 

EDD is a promising new FTICR technique, and is the negative ion complement to ECD. Both these electron-mediated techniques involve a radical ion intermediate, produced by either electron attachment to multiply charged cations (ECD) (Equations (48) and (49)) or electron removal from multiply charged anions (EDD) (Equation (50)). 

Current oscillations during the reduction of multiply charged anions for which the formation of passivating films could be excluded, such as... 

Yannouleas and Landman have theoretically considered the stability and decay channels of Au and Ag . They find that autodetachment dominates fission as the mode of decay at a finite temperature. Earlier they had studied sodium cluster dianions. These calculations show pronounced shell-effects in the second electron affinities illustrating the failure of the simple electrostatic model of charging a conducting sphere as depicted in Figure 1. However, the Coulomb barrier calculated with such simple assumptions probably is a reasonably good approximation. The importance of the Coulomb barrier in multiply charged anions is emphasized below. 

At present, there is no firm experimental evidence for dipole-bound dianions. However, it is instructive to consider the results of multiply charged anions of fullerene derivative clusters discussed in Section VI. Tuinman and Compton reported the formation of doubly charged anions of C6o(CN)2 dimers, [C6o(CN)2]J, in electrospray ionization. The dipole moment of the C6o(CN)2 molecule in which the two CN radicals are bonded to two adjacent carbon atoms in Cgo is expected to be large... 

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. 

Many molecules of acute chemical interest are charged in particular many species containing transition metal atoms are anions. Sometimes these anions are closed-shell, sometimes open-shell. There exists a formal proof that the solutions of the (differential, GUHF) Hartree-Fock equations actually exist for neutral systems and cations. The proof apparently cannot be extended to anions all that can be proved is that a molecule with n -t-1 electrons is stable if the net nuclear charge sum is n 4- where may be small but non-zero. This means that the existence of the solutions of the Hartree-Fock equations for anions is contingent on the particular case in some cases the solutions will exist, in other cases not. Clearly, it is extremely unlikely that the Hartree-Fock equations for multiply charged anions will exist. 

Another problem is for multiply charged anions which, in the gas phase, generate occupied MOs with positive energies which is physically unreasonable. In reality, such a condition should result in spontaneous ionisation but the finite extent of the basis functions does not permit an electron to escape into the ionisation continuum. 

Herron, W.J. Goeringer, D.E. McLuckey, S.A. Gas-phase electron-transfer reactions from multiply-charged anions to rare-gas cations. J. Am. Chem. Soc. 1995,117,11555-11562. 

Multiply charged anions are extracted with greater difficulty than the corresponding anions of lower charge, as shown in the series < HPC < H2PO4 and... 

Singly charged anions form weaker complexes with actinides generally than do multiply charged anions. The order of complex forming ability with some anions is... 

ScheUer MK, Compton RN, Cederbaum LS (1995) Gas-phase multiply charged anions. Science 270 1160-1166... 

Wang X-B, Wang L-S (1999) Experimental search for the smallest stable multiply charged anions in the gas phase. Phys Rev Lett 83 3402-3405... 

Wang X-B, Wang L-S (2000) Photodetachment of multiply charged anions the electronic structure of gaseous square-planar transition metal complexes PtX4 . 1 Am Chem Soc... 

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