Pi acid

The Lewis acid Hg3( i-C6F4)3 also forms a pi-acid/pi-base interaction with TR(carb). In addition to the crystal structure demonstrating the ABBABB pattern observed in other stacked materials which retain the aurophilic Au-Au interactions between four of the six basic Au(I) atoms of the BB moieties, studies have shown that the oligomeric acid/base interection is retained in solution. Pulsed gradient diffusion NMR studies [70] suggesting the oligomeric sizes and coupling... 

Based on the fact that pi-acids interact with the trinuclear gold] I) pi-bases, TR(carb) and TR(bzim), the trinuclear 3,5-diphenylpyrazolate silver(I) complex was reacted with each. Mixing [Au3(carb)3] or [Au3(bzim)3] with [Ag3(p,-3,5-Ph2pz)3] in CH2CI2 in stoichiometric ratios of 1 2 and 2 1 produced the mixed metal/mixed ligand complexes in the same gold-silver ratios. The crystalline products were not the expected acid-base adducts. It is suspected that the lability of the M-N bond (M=Au, Ag) in these complexes results in the subsequent cleavage of the cyclic complexes to produce the products statistically expected from the stoichiometry of materials used [74]. As a result of the lability of Au-N and Ag-N bonds, and the stability of... 

Composition of Indicator Solution PI Acid Alkaline Notes... 

Mulliken s general concept of charge-transfer complexes can be given explicit and quantitative reformulation in the NBO framework. This allows one to recognize the essential electronic continuity that relates CT complexes of different types, including H-bonded species (n-a CT complexes). Particular attention was paid to the interesting 7t-7t CT complexes of NO+ and related pi-acids, which exemplify the distinctive quantal dependence on the shapes of donor and acceptor orbitals. 

Lochmuller and coworkers used the formation of excimer species to answer a distance between site question related to the organization and distribution of molecules bound to the surface of silica xerogels such as those used for chromatography bound phases. Pyrene is a flat, poly aromatic molecule whose excited state is more pi-acidic than the ground state. An excited state of pyrene that can approach a ground state pyrene within 7A will form an excimer Pyr +Pyr (Pyr)2. Monomer pyrene emits at a wavelength shorter than the excimer and so isolated versus near-neighbor estimates can be made. In order to do this quantitatively, these researchers turned to measure lifetime because the monomer and excimer are known to have different lifetimes in solution. This is also a way to introduce the concept of excited state lifetime. 

Evidence Against Cell Wall pH and Isoperoxidase Specificity as Determinants of Isodityrosine Formation. To test these possible explanations for the exclusive formation of isodityrosine in the plant cell wall, samples of [14C]tyrosine were oxidized by H2O2 in the presence of three sharply contrasting horseradish-isoperoxidases [two low-pi (acidic) and one high-pi (basic)] at a wide range of pH values (37). 

Dianion formation may be avoided by limiting the amount of metal reductant or by using the latter to generate a weaker reductant such as the anion radical of a very weak pi acid (A) as in eq. (1). The latter may, in turn, be used to effect the one-electron reduction of the fluorescer (B) as in eq. (2). 

For emission studies, stilbene and naphthalene anion radicals have been successfully employed as the weak pi acid in this procedure.2... 

Add 125 pi TBA, vortex, and place for 15 min into a boiling water bath. Cool down in ice water and centrifuge fast at room temperature. Add 125 pi acid butanol, vortex twice for about 5 s each. Centrifuge for 10 min at 3000 rpm (2000xg). 

The ligand C2F4 would be expected to show some of the properties of a strong pi-acid . This appears to be the case from the structure of the complex [RhCl(PPh3)2(C2F4)] (D.XI). 

In their problem three basic binding motifs were considered relevant hydrogen bonds between selector and selectand, dipole stacking of the two amide moieties, and pi-pi stacking (charge transfer complexation) between the dinitro pi-acid portion of 1 with the pi-basic aminonaphthyl ring in 2. The motif code they used has the general form CnAs/nT/where ... 

Chem. Deserp. Partially polymerized (dimerized) rosin CAS 8050-09-7 EINECS/ELINCS 232-475-7 Uses Prep, of varnishes, driers, syn. resins, ink vehicles, floor tile, rubber compds., solder fluxes, elec, insulation oils, optical lens pilches, adhesives and protective coatings for food pkg./processing Features Noncrystallizing, high soften, pi., acidic resin Properties Gardner 8 (60% solids in min. spirits) solid, flakes sol. in aliphatic, aromatic, and chlorinated hydrocarbons, in ketones, esters, natural oils, terpenes, and varnish oils dens. 1.07 kg/l G-H vise. C (60% solids in min. spirits) Hercules drop soften, pt. 102 C flash pt. (COC) 218 C acid no. 144 sapon. no. 160 Polyplate 90 [Huber Engineered Materials]... 

Fairchild, R. M. and Holman, K. T., Selective anion encapsulation by a metalated cryp-tophane with a pi-acidic interior, /. Am. Chem. Soc., 2005,127,16364-16365. 

Hyun, M.H., Na, M.S., and Jin, J.S., Chiral recognition models for the liquid chromatographic resolution of pi-acidic racemates on a chiral stationary phase derived from iV-phenyl-Al-alkylamide of (5-naproxen), J. Chromatogr. A, 752, 77, 1996. 

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