Solution state complexes

The p-t-butylcalix[4]arenediquinone-bis(methylether) [56], which had previously been synthesized by Gutsche and co-workers, was used as a model compound in these studies. The receptors [54] and [55] have been shown by nmr titration techniques to form 1 1 solution state complexes with group 1 and 2 metal, ammonium and alkylammonium guest species. 

Solution State Complexes with Molecular Cations... 

Solution State Complexes with Neutral Molecules... 

Ghorab, M.K. Adeyeye, C.M. Elucidation of solution state complexation in wet-granulated oven-dried ibuprofen and P-cyclodextrin FT-IR and IH-NMR studies. Pharm. Develop, and Technology 2001, 6 (3), 315-324. 

The principal idea behind MIP synthesis is the generation of solution state complexes between the template ligand in hand and appropriate functional monomers, followed by subsequent freezing of these complexes by copolymerization of the above with an excess of a cross-linking monomer. These monomer-template complexes are stabilized by non-covalent interactions, reversible covalent interactions, or metal ion-mediated interactions. The types of interactions that are usually exploited in molecular imprinting are 1) cleavable covalent bonds 2) tt-tt interactions 3) hydrogen bonds 4) hydrophobic van der Waals interactions 5) crown-ether/cyclodextrin type interactions 6) metal-Ugand... 

The extensive hydrolysis of protactinium in its V oxidation state makes the chemical investigation of protactinium extremely difficult. Ions of protactinium(V) must be held in solution as complexes, eg, with fluoride ion, to prevent hydrolysis. 

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

This reaction is cataly2ed in solution by complexes of tungsten, molybdenum, or rhenium in high oxidation states, eg, Re ". Examples of active catalysts are... 

Solution State of Metal Complex Calixarenes and Polymeric Calixarenes... 

A reader familiar with the first edition will be able to see that the second derives from it. The objective of this edition remains the same to present those aspects of chemical kinetics that will aid scientists who are interested in characterizing the mechanisms of chemical reactions. The additions and changes have been quite substantial. The differences lie in the extent and thoroughness of the treatments given, the expansion to include new reaction schemes, the more detailed treatment of complex kinetic schemes, the analysis of steady-state and other approximations, the study of reaction intermediates, and the introduction of numerical solutions for complex patterns. 

The solutions of the structures of the Fe protein, the MoFe proteins, and the putative transition-state complex of these two proteins with ADP and A1F represent major advances in our understanding of ni-trogenase, but still many questions remain. 

The reaction between Fe(IlI) and Sn(Il) in dilute perchloric acid in the presence of chloride ions is first-order in Fe(lll) concentration . The order is maintained when bromide or iodide is present. The kinetic data seem to point to a fourth-order dependence on chloride ion. A minimum of three Cl ions in the activated complex seems necessary for the reaction to proceed at a measurable rate. Bromide and iodide show third-order dependences. The reaction is retarded by Sn(II) (first-order dependence) due to removal of halide ions from solution by complex formation. Estimates are given for the formation constants of the monochloro and monobromo Sn(II) complexes. In terms of catalytic power 1 > Br > Cl and this is also the order of decreasing ease of oxidation of the halide ion by Fe(IlI). However, the state of complexing of Sn(ll)and Fe(III)is given by Cl > Br > I". Apparently, electrostatic effects are not effective in deciding the rate. For the case of chloride ions, the chief activated complex is likely to have the composition (FeSnC ). The kinetic data cannot resolve the way in which the Cl ions are distributed between Fe(IlI) and Sn(ll). 

Relatively few investigations involving palladium carbonyl clusters have been carried out, partly because palladium per se does not form stable, discrete homometallic carbonyl clusters at room temperature in either solid or solution states.114,917-922 Nevertheless, solution-phase palladium carbonyl complexes have been synthesized with other stabilizing ligands (e.g., phosphines),105,923 and carbon monoxide readily absorbs on palladium surfaces.924 Moreover, gas-phase [Pd3(CO)n]-anions (n = 1-6) have been generated and their binding energies determined via the collision-induced dissociation method.925... 

Exciplexes are complexes of the excited fluorophore molecule (which can be electron donor or acceptor) with the solvent molecule. Like many bimolecular processes, the formation of excimers and exciplexes are diffusion controlled processes. The fluorescence of these complexes is detected at relatively high concentrations of excited species, so a sufficient number of contacts should occur during the excited state lifetime and, hence, the characteristics of the dual emission depend strongly on the temperature and viscosity of solvents. A well-known example of exciplex is an excited state complex of anthracene and /V,/V-diethylaniline resulting from the transfer of an electron from an amine molecule to an excited anthracene. Molecules of anthracene in toluene fluoresce at 400 nm with contour having vibronic structure. An addition to the same solution of diethylaniline reveals quenching of anthracene accompanied by appearance of a broad, structureless fluorescence band of the exciplex near 500 nm (Fig. 2 )... 

The Gd-H distance, /-GdH, which enters at the inverse sixth power into the expression of inner-sphere relaxivity, is a difficult parameter to obtain experimentally. It is generally estimated on the basis of Gd-coordinated water oxygen distances, determined by solid-state X-ray analysis. Solid-state distances are good estimates of the aqueous solution state, as was experimentally proven by an X-ray absorption fine-structure study on [Gd(D0TA)(H20)] and [Gd(DTPA)(H20)]2, which gave identical values for the Gd-0 distances for both complexes in solid and solution states.20... 

Fig. 6.21. Principle of detection of lipopolysaccharide (LPS) with the CD14-derived probe. It relies on the formation of a ground state complex between fluorescein and rhodamine in aqueous solution with quenching of donor and acceptor fluorescence. Spectrum A shows hypothetical fluorescence emission spectra of this complex. After LPS binding, the peptide sequence gets straightened prohibiting the close contact between the two fluorophores and leading to the recovery of red fluorescence (Spectra B).

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