K Complexes

FIGURE 10.40 The structures of (a) the vahuomyciu-K complex and (b) uucom-plexed vahuomychi. 

K-K Complexation Hydrogen bonding Inclusion Dipole stacking Steric interactions Anionic or cationic binding... 

Fig. 10. Representation of the mechanism of redox driven K + transport using an electron and a cation carrier. (59-Ni°) and (59-Ni ) are the oxidized and reduced form of the electron carrier, the nickel bis-dithiolene complex 59 [] and [K+] are dicyclohexyl-18-crown-6 and its K+ complex. (Cited from Ref. 59>)...

Fig. 21. Crystal structure of the Valinomycin-K+ complex. Reproduced with permission from Ref.100). This crystal structure confirmed within tenths of an Angstrom the structure derived previously in solution 97 98) and by means of conformational energy calculations...

Fig. 23. Space filling model of the Enniatin B—K + complex after the crystal structure 103). Since the carbonyl moieties coordinating the cation are similar for Enniatin B and Valinomycin, the difference in selectivities must arise due to the energetics of the conformations required to achieve coordination of the cation...

Sleep spindles and K complexes in a background EEG that has less than 20% delta activity None Decreased from wake... 

In the case of the Na+ and K+ complexes of N9-ethyladenine-aza-18-crown-6, the metal ions exhibit different types of interaction at the minor groove site N3 (Fig, 14) (52). The Na+ complex, 6, shows a second-sphere interaction involving the coordinated H20 hydrogen bonding to N3 [Na-OH2 2.327, H0 N3 2.836 A], In contrast, the K+ complex, 7,... 

The most accurate energies and geometries for the Cl" + CH,Clb system are those calculated at the CEPA-l/avtz and G2(+) levels of theory. Without zero-point energies included, the CEPA- 1/avtz calculations give a complex well depth of-10.6 kcal/mol and a central barrier height of 2.8 kcal/mol. The G2(+) values for these energies are -10.7 and 3.0 kcal/mol. The most recent experimental value for the 0 K complex well depth is 12.2 2 kcal/mol.23... 

With collection for kinetic shift, the two lowest frequencies are 30 cm"1 for both K and Na complexes. With correction for kinetic shift, the two lowest frequencies are 10 cm"1 for Na complexes and 5 cm"1 for K complexes. This set is considered to be the best. For a discussion, see Klassen et al.64 Experimental determinations based on ion-molecule equilibria, Sunner et al.94 Theoretical calculations, HF/6-31G, combined with a semiempirical correction. Roux and Karp us.,5c Theoretical calculations, HF/6-31G, combined with a semiempirical correction. Roux and Karplus.,5c Theoretical calculations, 6-31+G(2d) MP2, Jensen.93 Succinamide. 

Nakamura H., Takagi M., Ueno K., Complexation and extraction of alkali metal ions by 4 -picrylaminobenzo-18-crown-6 derivatives, Anal. Chem. 1980 52 1668. 

Once again, such species yield Na+ and K+ complexes which are more stable than complexes of their unsubstituted analogues. This is illustrated in Table 4.1 for the case where n = 2 the Table summarizes log/C values... 

Table 4.1. Log K values for Na+ and K+ complexes of ligandsof type (183 n = 2) in methanol3...

The stability of cryptate complexes. The cage topology of the cryptands results in them yielding complexes with considerably enhanced stabilities relative to the corresponding crown species. Thus the K+ complex of 2.2.2 is 105 times more stable than the complex of the corresponding diaza-crown derivative - such enhancement has been designated by Lehn to reflect the operation of the cryptate effect this effect may be considered to be a special case of the macrocyclic effect mentioned previously. 

The thermodynamic data for K+ complexes of dibenzo-18-crown-6 [11] in aprotic solution show that AAG + AGU (K+) changes with solvent (Table 16). Although the data have been collected from several sources, they would seem to indicate that the cation is more exposed to interactions with the solvent in crown-ether complexes than in cryptates. Hence, the term... 

Free energies of transfer" of K+ complexes of dibenzo-18-crown-6 [11] and [2.2.2]-cryptand 137] from water to non-aqueous solvents at 25°C... 

To confirm that displacement of the complexed K+ by other metals did not occur, thedye/K+ complex was exposed to other metal ions. Although some variation in the fluorescence signal was observed, it was attributed to fluctuations in the fluorescence quantum yield of the dye due to changes in the ionic strength of the solution. There was clear evidence, however, to indicate ion selectivity. 

Nakamoto K. Complexes of alkoxides, alcohols, ethers, ketones, aldehydes, esters and carboxylic groups, in Infrared and Raman spectra of inorganic and coordination compounds, Wiley, 2009, 62-67. 

From the kinetic traces for the slow k complexes, we precisely mapped out the difference spectrum for the intermediate state relative to the ground state [8b]. Comparison with the static spectrum expected for the intermediate later revealed that for these complexes, the size of the kinetic ET intermediate was only ca. 20% of the size predicted from knowledge of the static spectra. We therefore remeasured the I A kinetics with improved instrumentation [27], Figure 13 shows the time evolution of state I for the [ZnCcP, Cc (horse)] complex. The intermediate [I] not only decays more slowly than kp (Fig. 13... 

The effects of valerian in poor sleepers was studied comparing it to placebo controls (Schulz et al. 1994). Valerian showed an increase in slow-wave and a decrease in stage 1 sleep. K-complex density was increased, but REM was unaltered, and no effects were reported on subjective sleep quality. 

Pirkanniemi, K., Complexing Agents A Study of Short-term Toxicity, Catalytic Oxidative Degradation and Concentrations in Industrial Waste Waters. Kuopio University Publications C. Natural and Environmental Sciences, 209, 2007, Doctoral dissertation. Finland. 

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