Multiply charged ions, charge transfer

Partial charge-transfer reaction. An ion/neutral reaction that reduces the charge on a multiply charged reaction ion. 

The most important multiply charged polyatomic positive ions are compounds with two or more basic groups which when protonated lead to doubly or poly-charged ions. Typical examples are diamines such as the double protonated a, to alkyldiamines, H3N(CH2)pNH2+, and the most important class, the polyprotonated peptides and proteins, which have multiple basic residues. Charge reduction for these systems occurs through proton transfer from one of the protonated basic sites to a solvent molecule. Such a reaction is shown below for the monohydrate of a doubly protonated diamine ... 

Equilibria Where a Neutral Molecule Is Exchanged. The difficulties discussed above for proton transfer and electron transfer equilibria involving multiply charged ions are not present when neutral molecules (ligands) which are complexed to a given ion are exchanged. Equation 43 is a typical example ... 

Williams, E.R. Proton Transfer Reactivity of Large Multiply Charged Ions. J. Mass Spectrom. 1996, 31, 831-842. 

CHARGE TRANSFER IN NEUTRAL ATOM-MULTIPLY CHARGED ION... 

The electron transfer in neutral atom-multiply charged ion collisions... 

The cross-section of electron transfer to a multiply charged ion can be calculated by solving a set of coupled equations which take into account the probability of electron transfer on to different levels. Such calculations are extremely tedious (for a review, see ref. 21). At the same time, the presence of transitions into a large number of states makes it possible to describe the charge transfer in terms of the formalism, based on the idea of electron tunneling from one potential well to another. Using such an approach, Chibisov [22] has obtained an analytical expression for the charge transfer cross-section. 

During slow collisions, the main contribution to the charge transfer cross-section is made by the impact parameters which exceed the size of a neutral atom. In this case, the potential barrier for tunneling is mainly formed by the electric field of the multiply charged ion in the vicinity of the neutral atom (Fig. 8). This field is equal to F = zjR2. The probability of... 

It is important to note that the electrode potential is related to activity and not to concentration. This is because the partitioning equilibria are governed by the chemical (or electrochemical) potentials, which must be expressed in activities. The multiplier in front of the logarithmic term is known as the Nernst slope . At 25°C it has a value of 59.16mV/z/. Why did we switch from n to z when deriving the Nernst equation in thermodynamic terms Symbol n is typically used for the number of electrons, that is, for redox reactions, whereas symbol z describes the number of charges per ion. Symbol z is more appropriate when we talk about transfer of any charged species, especially ions across the interface, such as in ion-selective potentiometric sensors. For example, consider the redox reaction Fe3+ + e = Fe2+ at the Pt electrode. Here, the n = 1. However, if the ferric ion is transferred to the ion-selective membrane, z = 3 for the ferrous ion, z = 2. 

Toshima, N. (1994) Ionization and charge transfer of atomic hydrogen in collision with multiply charged ions, Phys. Rev. A, 50, pp. 3940-3947. 

To bring the power of ECD to ion trap analysers, a new ECD-like activation method has been developed [58]. This method, which is called electron transfer dissociation (ETD), uses gas-phase ion/ion chemistry to transfer an electron from singly charged aromatic anions to multiply charged ions. The mechanism of this method and the observed fragmentation pathways are analogous to those observed in ECD. 

Charge Transfer Involving Multiply Charged Ions. 267... 

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