Cu-phenanthroline

Fig. 4.68 Cu-phenanthroline-DBAD catalyzed aerobic oxidation of alcohols.

Lipids may well be involved in the subunit interactions in the Na-K ATPase complex, since this would explain why the monomeric K -activated phosphatase is less inhibited upon delipidation and is reactivated at lower lipid concentrations than the overall Na-K ATPase activity [117,120]. This requirement of subunit interaction is supported by the finding that in the presence of detergents covalent cross-linking of a-subunits by Cu or Cu -phenanthroline is inhibited and is replaced by cross-linking of an a- to a )8-subunit [121], despite the very low SH-group content of the j8-subunit (Section 3a). In a lipid-depleted enzyme preparation the ATP-dependent phosphorylation level is reduced less than the overall Na-K ATPase activity [122]. Addition of K to the phosphorylated lipid-depleted enzyme did not stimulate Pj production, whereas addition of K to the lipid-reactivated preparation increased hydrolysis. This implies that the P 2 — P conformational transition is blocked in the lipid-depleted preparations, and that this is one of the steps in which subunit interaction is involved. 

Exciplexes and Second Sphere Interactions The concept of exdplex formation in inorganic systems has received considerable attention in recent years. Exciplexes can be observed when ground state complex formation is forbidden but the excited state complex has a shallow energy minimum that can radiatively decay to the ground state (Equation (6) and (7)). McMillin and co-workers postulated exdplex contributions to nonradiative relaxation of Cu phenanthroline... 

Copper (I) complexes exhibit catalytic activity for the four-electron (4-e) reduction of O2 to water. Natural occurring enzymes like Cu-containing fungal laccase reduce O2 directly to water very efficiently at very positive potentials, not far from the thermodynamic standard potential of the O2/H2O couple. These enzymes involve a trinuclear Cu active site [149-153]. For this reason some authors have investigated the catalytic activity of Cu(I) complexes for ORR, in particular Cu phenanthrolines confined on graphite or glassy carbon surfaces [154-169], with the aim of achieving the total reduction of O2 via the transfer of four-electrons. 

Chidsey et al. [169] have also studied the catalytic activity of a Cu(I) complex of 3-ethynyl-phenanthroline covalently attached to an azide-modified glassy carbon electrode. This catalyst promotes the four-electron reduction of O2 at pH 4.8 (acetate buffer). In contrast to what is observed by Anson et al. [156-158, 170] using Cu phenanthroline, Chidsey et al. found a second-order dependence of the rates on Cu coverage at moderate overpotentials. This suggests that O2 interacts with two Cu centers simultaneously, forming a bridge structure, as illustrated in Fig. 7.33. 

The Cu / phenanthroline strategy to prepare novel supramolecular architectures, as exemplified by the synthesis of a simple catenane. Sau vage, J.-P. "Transition Metal-Containing Rotaxanes and Catenanes in Motion Toward Molecular Machines and Motors." Acc. Chem. Res., 31,611-619 (1998). 

Electrophilic activation can occur by both metal coordination and hydrogen bonding, and it is common for enzymes to combine these effects. Less common are synthetic systems that combine these, but one particularly simple example is the use of the diaminophenanthroline-Cu(II) complex shown below. This compound accelerates the hydrolysis of 2, 3 -cAMP(cAMP = cyclic adenosine monophosphate) approximately 20,000-fold compared to a Cu-phenanthroline complex with the amino groups replaced by methyls. 

In 2011, Goossen and coworkers [38] also reported a one-pot three-component protocol for the synthesis of azomethines, starting from simple, nontoxic precursors - that is, potassium a-oxo car-boxylates, aryl halides, and primary amines (Scheme 3.21). In the presence of the bimetallic system, Cu/phenanthroline, and Pd/l,l -bis(diphenylphosphino)ferreocene (dppf) a wide range of valuable imines were obtained in good yields at 100 °C (Scheme 3.21). Interestingly, all three substituents in the azomethine products could be individually varied. 

Proof of Concept LGA Provided by a Cu" Phenanthroline in the Solvolysis of Closely Positioned tri-, di-, and Monophosphates... 

Figure 3.2. Crystal structures of (upper left) Cu(L-tryptophan)(2,2 bipyridine) CIO 4 (upper right) Cu(L-Tryptophan)(1, l()-phenanthroline)ClO4 . 5H2O and (lower) Cu(L-...

Cu, Ni, Co, Cr, Fe, or Al, even in traces, must be absent when conducting a direct titration of the other metals listed above if the metal ion to be titrated does not react with the cyanide ion or with triethanolamine, these substances can be used as masking reagents. It has been stated that the addition of 0.5-1 mL of 0.001 M o-phenanthroline prior to the EDTA titration eliminates the blocking effect of these metals with solochrome black and also with xylenol orange (see below). 

Ethyl 6-methyl-4-phenyl-2-(phenylthio)-l,4-dihydropyrimidine-5-carboxyla-te was easily synthesized from ethyl 6-methyl-4-phenyl-2-thioxo- 1,2,3,4-tetra-hydropyrimidine-5-carboxylate and phenylboronic acid via microwave-assisted Cu-mediated S-phenylation (Scheme 108) [107]. The reaction involves the use of a stoichiometric amount of Cu(OAc)2 and a two-fold excess of 1,10-phenanthroline as a hgand. 

Preconcentration of metal cations is also achieved by providing ligand binding sites in polymer layers, e.g. 4-methyl-4 -vinyl-2,2 -bipyridine for Fe " and Cu ". Carbon paste electrodes containing dimethylglyoxime or o-phenanthroline... 

These are thermodynamically relatively weak oxidants (Table 18) and their action is relatively restricted, for example, to inorganic ions of moderate reducing power such as iodide, to polyfunctional organic compounds such as hydroxy-acids, and, in the cases of Ag(I) and Cu(II), to CO and H2. Fe(III) is particularly affected by hydrolysis and all these oxidants form complexes with suitable ligands. Cyanide ion and 1,10-phenanthroline form strong complexes with Fe(III) which greatly affect its behaviour. Tris-l,10-phenanthrolineiron(III) (ferriin) displays... 

In the presence of sufficient FeY then / i[FeY ]Ar4[FeY ] and the kinetics observed with added FeY result. Phenanthroline removes all Fe(II) from solution thereby suppressing the back-reaction in (71) and the change in order is explained. Cu(II) exerts a catalytic effect, as in the oxidation by ferric ion, by oxidising N2H3, thereby reducing the importance of the back-reaction. 

For the installation of the pyrrolidinylethanol moiety 10 on the aryl group, we first tested Buchwald s Cu-catalyzed conditions with 10, aryl iodide 12, Cs2C03, Cul and 1,10-phenanthroline at 110°C in toluene to prepare the penultimate 49 [14a], The reaction was very slow, giving only 5-10% conversion even after 2 days. The reaction was faster at higher temperatures but two impurities 50 and 51 were observed (Scheme 5.14). To find the optimal conditions, xylene and diglyme were tested as solvents, lithium, potassium and cesium carbonates were screened as bases and 2,2 -bipyridy], TMEDA and l-(2-dimethylaminoethyl)-4-methylpiperazine were examined as ligands. The optimized protocol was identified as 10mol% of... 

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