Metal substitution, effect

Instead of the surface area or the free volume, the authors found that MOFs such as Mg/DOBDC and Ni/DOBDC with a high density of open metal sites are promising candidates for CO capture from flue gas in, which CO partial pressure is about 0.1 atm. Caskey et al. [43] found that metal substitution in the DOBDC series can significantly impact their CO capacities in the low-pressure region. The metal substitution effect m be caused by the differences in the ionic character of the metal-oxygen bonds in the DOBDC-series MOFs. Liu et al. found that Ni/DOBDC has a higher CO capacity than NaX and 5A zeolites at 0.1 atm, and 25° C. In addition, water does not affect CO adsorption in the Ni/DOBDC as much as in NaX and 5A zeolites, and it is much easier to remove water from Ni/DOBDC by heat regeneration [44]. Therefore, the Ni/DOBDC can adsorb more CO than traditional zeolites under the same moist conditions. 

Metal hydroxides of first- and second-group elements can enhance ortho substitution, the degree of which depends on the strength of metal-chelating effects linking the phenolic oxygen with the formaldehyde as it approaches the ortho position. Transition metal ions of elements such as Fe, Cu, Cr, Ni, Co, Mn, and Zn as well as boric acid also direct ortho substitutions via chelating effects (Fig. 7.9). 

FIGURE 8.9. Linear free-energy relationship for the effect of metal substitution on e2 and e3 in staphylococcal nuclease (see text for details). 

Carotenoids incorporated in metal-substituted MCM-41 represent systems that contain a rapidly relaxing metal ion and a slowly relaxing organic radical. For distance determination, the effect of a rapidly relaxing framework Ti3+ ion on spin-lattice relaxation time,and phase memory time, Tu, of a slowly relaxing carotenoid radical was measured as a function of temperature in both siliceous and Ti-substituted MCM-41. It was found that the TM and 7) are shorter for carotenoids embedded in Ti-MCM-41 than those in siliceous MCM-41. 

The above substitution effects appear to be independent of the nature of the ligand (16) since the benzyl compounds behave similarly, Table XI. It would appear from these observations that the introduction of anionic ligand would be sufficient to increase activity of transition metal alkyl compounds for polymerization. This, however, is probably an oversimplifica-... 

Over the past 20 years, the principal biomedical application for (free or metal-substituted) porphyrins has been Photodynamic Therapy (PDT), with extensive literature in the area including a number of comprehensive reviews (114-116). Porphyrins offer scope for optical imaging as they are potent fluorophores in the red region of the electromagnetic spectrum. Although, to date, the emphasis has been on their therapeutic effects, due to their... 

Metal-substituted hemoglobin hybrids, [MP, Fe " (H20)P] are particularly attractive for the study of long-range electron transfer within protein complexes. Both photoinitiated and thermally activated electron transfer can be studied by flash excitation of Zn- or Mg-substituted complexes. Direct spectroscopic observation of the charge-separated intermediate, [(MP), Fe " P], unambiguously demonstrates photoinitiated ET, and the time course of this ET process indicates the presence of thermal ET. Replacement of the coordinated H2O in the protein containing the ferric heme with anionic ligands (CN , F , Nj ) dramatically lowers the photoinitiated rate constant, k(, but has a relatively minor effect on the thermal rate, kg. 

Kim S-J (2007) Substitution effects in binary intermetallic compounds investigations in the system alkali and alkaline-earth metal - tin and alkaline-earth metal - bismuth. PhD Thesis, Technische Universitat Miinchen, Miinchen... 

PtI MeC6H3(CH2NMe2)2-o,o ]BF4 (49) is considered to be a metal-substituted arenonium ion it should be susceptible to nucleophilic attack. This concept has been used to effect a fully reversible, aryl to cyclohexadiene conversion in a metal coordination sphere.524... 

A comparison of Figs. 5 and 6 shows that between the anionic polymerization of styrene and the transition metal polymerization of styrene there is a region of poor catalysts which produce either atactic or no polymers. It has been shown by the substitution effects of the reaction that both the styryl anion and the styryl cation propagate on the... 

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