Complexes cation-base

The cation plays a prominent structure-directing role in zeolite crystallization. The unique structural characteristics of zeolite frameworks containing polyhedral cages (62, 63) have led to the postulate that the cation stabilizes the formation of structural subunits which are the precursors or nucleating species in crystallization. The many zeolite compositions and complex cation base systems studied allow a test of the structuredirecting role of the cation and the cation templating concept. Table I summarizes the cation base systems from which zeolites have been synthesized. The systems used before 1969 are indicated to illustrate the number and complexities of new cation systems investigated since that time. Table II presents a summary of zeolite framework structure types, the cation systems in which they have been formed, and a proposal for a cation specificity for the formation of each framework type. A similar... 

JA5190, 940M5132). Proton abstraction from 109 gives a neutral ti C) 2-thienyl complex, 110. Such a reaction becomes impossible in case of the 2,5-dimethylthiophene analog of 109. However, use of a strong base such as potassium hydroxide in methanol gives 111. An attempted transformation of 109 to 110 by protonation with triflic acid leads, however, to the thienylcarbene complex cation 112 where the aromaticity is disrupted. 

In this review, recent development of active transport of ions accross the liquid membranes using the synthetic ionophores such as crown ethers and other acyclic ligands, which selectively complex with cations based on the ion-dipole interaction, was surveyed,... 

Recently, we [13,14] evidenced by ATR-IR spectroscopy that the membrane potential of ionophore-incorporated, PVC-based liquid membranes is governed by permselective transport of primary cations into the ATR-active layer of the membrane surface. More recently, we [14 16] observed optical second harmonic generation (SHG) for ionophore-incorporated PVC-based liquid membranes, and confirmed that the membrane potential is primarily governed by the SHG active, oriented complexed cations at the... 

The retrosynthetic analysis of the 2-oxygenated carbazole alkaloids, 2-methoxy-3-methylcarbazole (37) and mukonidine (54), based on an iron-mediated approach, led to the iron-complexed cation 602 and the arylamines 655 and 656 as precursors (Scheme 5.48). 

The retrosynthetic analysis of the 2-oxygenated carbazole alkaloids, 2-methoxy-3-methylcarbazole (37), O-methylmukonal (glycosinine) (38), 2-hydroxy-3-methylcar-bazole (52), and mukonal (53) based on the molybdenum-mediated approach led to the molybdenum-complexed cation (663) and 3-methoxy-4-methylaniline (655) as precursors (Scheme 5.51). The cationic molybdenum complex, dicarbonyl (ri -cyclohexadiene)(r -cyclopentadienyl)molybdenum hexafluorophosphate (663), required for the electrophilic substitution, was easily prepared quantitatively through known literature procedures (586,587). 

The activation parameters are presented in Table 819 For the reactions be between the Co(III) complex2+ and Fe-edta2-, (a) to (c) in Table 8, the activation enthalpy is smaller and the activation entropy larger than for the reduction by Fe2+, (d) to (f), which is a reaction of two cations. A comparison of the parameters for the polymer complex, (b) or (c), with those for the pyridine complex, (a) shows that the acceleration for the PVP or QPVP complex is based on a decrease in activation enthalpy and an increase in activation entropy. This is the opposite of the polyelectrolyte-catalyzed reaction, in which the acceleration is due to an increase in activation entropy (compare(e) with (d)). In the polyelectrolyte-catalyzed system the acceleration and increase in activation entropy are attributed to the increase in the local concentration of the two reactants, the Co(HI)-Py complex2 and Fe2+ 84, whereas in the reaction of the polymer complex the large activation entropy and small activation enthalpy are held to be due to the increase in the local concentration of the reactant Fe(II)-edta2 and the electrostatic attraction between the reactant and the Co(III) complex, which is fixed to the polycation chain. 

Extremely strong base. Has excellent solublizing properties, and complex cation so that the anion is more reactive. 

The quantum yield of the [Ru(bpy)3]2 + photosensitized reduction of Co(III)-Schiff base complex cation in aqueous solution is greately affected by the composition of the polymer-supported polyanionic donors such as vinylbenzylamine-iV,iV-diacetate-... 

Kircheis, R., Schuller, S., Brunner, S., Ogris, M., Heider, K.H., Zauner, W. and Wagner, E. (1999) Poly cation-based DNA complexes for tumor-targeted gene delivery in vivo. J. Gene Med., 1, 111-120. 

The X-ray structure of the L-Sr(Picrate)2 (L = p-tert-butyl-calix[4]arene-tetra(diethylamide)) is reported, as well as MD simulations on the L M2+ complexes in vacuo, in water, and in acetonitrile solutions for alkaline earth cations with a comparison of converging and diverging conformers.130 In the simulated and solid-state structures of the L M2+ complex, the ligand wraps around the complexed cations M2+ (more than it does with alkaline cations), which are completely encapsulated within the polar pseudo-cavity of L, without coordination to its counterion in the crystal or to solvent molecules in solution. In contrast to alkali cation complexes, which display conformational flexibility in solution, computations show that the alkaline earth cation complexes are of the converging type in water and in acetonitrile. Subtle structural changes from Mg2+ to Ba2+ are observed in the gas phase and in solution. Based on FBP calculations, a binding sequence of alkaline earth cations was determined Mg2+ displays the weakest affinity for L, while Ca2+ and Sr2+ are the most stable complexes, which is in agreement with the experiment. 

This tendency to react with a range of nucleophiles is reflected in the general rate equation for reactions of this type, as seen for the hydrolysis of [Co(en)2(H2NCH2C02 Pr)]3+. Typically, a three-term rate equation is obtained. This is indicative of a process in which at least three parallel reaction pathways are being followed. In the case of the hydrolysis of [Co(en)2(H2NCH2C02 Pr)]3+, the kx term refers to attack of the chelated ester by water, the k2 term to attack by hydroxide and the /% term to general base attack by any other nucleophile which is present in solution. The rate is defined in terms of the loss of the starting complex cation, rather than the formation of any specific product of the reaction. 

Solvent dyes [1] cannot be classified according to a specific chemical type of dyes. Solvent dyes can be found among the azo, disperse, anthraquinone, metal-complex, cationic, and phthalocyanine dyes. The only common characteristic is a chemical structure devoid of sulfonic and carboxylic groups, except for cationic dyes as salts with an organic base as anion. Solvent dyes are basically insoluble in water, but soluble in the different types of solvents. Organic dye salts represent an important type of solvent dyes. Solvent dyes also function as dyes for certain polymers, such as polyacrylonitrile, polystyrene, polymethacrylates, and polyester, in which they are soluble. Polyester dyes are principally disperse dyes (see Section 3.2). 

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