Cation donor

Ashwell GJ, Chwialkowska A (2006) Controlled alignment of molecular diodes via ionic assembly of cationic donor-(pi-bridge)-acceptor molecules on anionic surfaces. Chem Commun 1404-1406... 

In nature, dissolution caused by carbonic and sihcic acids is a slow process. Because formation of carbonate and silicate complexes is very slow and mostly occurs on a geological time scale, it is difficult to reproduce the necessary reactions in the laboratory. On the other hand, acid-base cements may be produced within hours, and controlling the rate of reaction in these materials is easier than accelerating reactions in carbonate and sihcate minerals. Acid-base cements have considerable potential for commercial applications by exploiting the solubility of cation donors of oxides in acidic solutions. For this reason, we next explore the dissolution steps involved in formation of these cements in more detail. 

As early as 1950, Kingery [62] explored formation of generalized CBPCs by reacting phosphoric acid solution with different cation donor oxides. He performed this study in order to identify reactions that may lead to CBPCs as precursors to refractories. He determined, in each case, whether the reaction sets into a ceramic, and if it does, what is the setting time and maximum temperature on a 0.5 cm sample. Using the X-ray diffraction technique, he also tried to identify the phases in the set ceramic. 

We have already discussed use of silicates as cation donors in forming CBPCs. In a manner similar to use of silicates, Sychev et al. [64], and Sudakas et al. [65] showed that... 

Overall the cation donors remain the key parameter in determining formation of the ceramics in a diluted or partially neutralized phosphate solution. For this reason, Chapters 4-6 are devoted to a dissolution model for the formation of these ceramics. In Chapters 9-13, this model will then be used to discuss formation of ceramics from common oxides. 

Sugama and Allan [5] used calcium aluminates (tricalcium aluminate, C -A, monocalcium aluminate, C A, or calcium dialuminate, C A2) as the cation donors and reacted them with an ammonium polyphosphate fertilizer solution and formed quicksetting cements. The purpose of this study was to develop cements that are not affected by the CO2 environment and are useful as downhole cements in geothermal wells (see Chapter 15). The composition of the fertilizer was 11.1 wt% N as ammonia, 37.0 wt% P2O3, 50.79 wt% water, and the rest trace elements. Differential scanning calorimetry (DSC) showed that the reaction rates of the three minerals are in the decreasing order ... 

Moreover, the facile bimolecular reactions of the cationic donor RH and/or the anicmic acceptor A, especially with additives diat are present during oxidation, can accomplish the same displacement of the redox equilibria in measure with the competition from back electron transfer. For example, the arene activation with nitrosonium ion merely reaches a low steady-state concentration of the radical pair, which persists indefinitely in equation (13). However, oxygen r idly tnq>s even small amounts of nitric oxide to render back electron transfer ineffective, and successfully effects aromatic nitration (Scheme 3). ... 

Figure 2.30 Representation of the asymmetric unit of [Nd(L )4(H20)][(TTF—CH=CH—Py+)] 2-The radical cation donors are drawn as balls and sticks the paramagnetic anionic coordination complexes of Nd(III) are drawn as capped sticks [23d], (Reprinted with permission from F. Pointillart, O. Maury, Y. Fe Gal, S. Golhen, O. Cador and F. Ouahab, 4-(2-Tetrathiafulvalenyl-ethenyl)pyridine (TTF—CH=CH—py) radical cation salts containing poly(P-diketonate) rare earth complexes synthesis, crystal structure, photoluminescent and magnetic properties, Inorganic Chemistry, 48, 7421-7429, 2009. 2009 American Chemical Society.)...

Alkali metals themselves may function as electron (and cation) donors [85] providing an alternative source of M when in contact with monomer. 

Historically, this is the original definition of what is meant by an acid or a base. It is also the one with which you are most likely to be familiar. An acid is a hydrogen cation donor, while a base is a hydroxide anion donor. 

They usually require a co-catalyst, such as water, an organic acid, a halogen acid, or an organic halide, which serves as the proton or cation donor as it associates with the Lewis acid (Eq. 22.10-22.12). 

Whereas the aryllead(IV) tricarboxylates in the above mentioned arylation reactions of electron-rich arenes act as aryl-cation donors, in the palladium-catalysed cross-... 

When the attempt is made to reach definitions independent of a solvent they become similar to those given by Ussanovich s according to which an acid is either a cation donor or an anion acceptor, and a base either an anion donor or a cation acceptor. In this way certain redox reactions are also considered as acid-base reactions. 

Figure 15 The asymmetric unit of [La(L )5][(TTF-CH=CH-Py +)]2 - The radical cation donors are drawn as balls and sticks the anionic coordination complex of La(III) is drawn as capped sticks. (Reprinted with permission from Ref. 12. Copyright (2009) American Chemical Society.)...

---