The Potential for Unique Chemistry

The properties of the lanthanide elements and their organometallic complexes described in the previous section explain in part why organo-met lic chemists in the past found lanthanide chemistry much less interesting than transition metal chemistry. The highly ionic, trivalent organolanthanide complexes appeared to have little potential to interact with the small-molecule substrates that provide such a rich chemistry for the transition metals neutral unsaturated hydrocarbons, H2, CO, phosphines, etc. The two-electron oxidation reduction cycles so important in catalytic transition metal chemistry in 18 16 electron complexes seemed 

The large size and ionic, electropositive character of the lanthanides, properties which make the chemistry experimentally difficult, also make the lanthanides strongly electrophilic and oxophilic. These properties can also impart unusual chemistry. 

In summary, the special combination of physical properties of the lanthanides should translate into novel and potentially useful chemical behaviour. As stated in an earlier summary of organolanthanide chemistry 14), the challenge in the lanthanide area, therefore, is to place the lanthanide metals in chemical environments which allow exploitation of their chemical uniqueness. In the past 5 years, organometallic environments beyond the simple, original, tris(cyclopentadienyl) and bis(cyclo-pentadienyl) chloride and alkyl types have been explored and some remarkable chemistry has resulted. 

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With almost all of the conceivable coordination chemistry of the expanded porphyrins still left to be explored, it cannot be over-stres that the potential for new chemistry is enormous. This is i rticularly true when account is made of the fact that the chemistry of the metalloporphyrins has played a dominant role in modern inorganic chemistry. What with the possibility to enhance the stability of imusual coordination geometries (and, perhaps oxidations states) and the ability to form stable coordination complexes with a variety of unusual cations including those of the lanthanide and actinide series, the potential for new inorganic and organometallic discoveries are almost unlimited. For instance, as with the porphyrins, one may envision linear arrays of stacked expanded porphyrin macrocycles which may have unique conducting properties and/or which could display beneficial super- or semiconducting capabilities. Here, of course, the ability to coordinate not only to cations but also to anions could prove to be of tremendous utility. 

The results reported here indicate the potential for Bronopol (Myacide AS) as a preservative in mineral slurry systems. In particular, its ability to control organisms that are tolerant or resistant to other biocide chemistries is a valuable feature. Sondossi et alf" have reported on the activity of Bronopol against organisms that are resistant to formaldehyde. The results presented here indicate that this ability also covers BIT resistant organisms. The explanation for this may be related to some unique facet of Bronopol s mode of action and this fact is supported by published work. Overall, it suggests that Bronopol could be used in clean-up regimes to recover contaminated product. 

These examples of functionalization of carbon nanotubes demonstrate that the chemistry of this new class of molecules represents a promising field within nanochemistry. Functionalization provides for the potential for the manipulation of their unique properties, which can be tuned and coupled with those of other classes of materials. The surface chemistry of SWCNTs allows for dispersibility, purification, solubilization, biocompatibility and separation of these nanostructures. Additionally, derivatization allows for site-selective nanochemistry applications such as self-assembly, shows potential as catalytic supports, biological transport vesicles, demonstrates novel charge-transfer properties and allows the construction of functional nanoarchitectures, nanocomposites and nanocircuits. 

Stellacyanin, the plastocyanins, and the azurins are the most widely studied copper-containing metalloproteins of the next active-site class, the Blue Copper sites. These proteins, which generally appear to be involved in redox chemistry, have quite unique spectral features32,33). The potential for complementary interaction between inorganic spectroscopy and protein crystallography is well demonstrated by the roles that they have played in generating fairly detailed geometric and electronic structural pictures of the Blue Copper metal centers. 

The unique features of dendritic architecture and the rich chemistry of organo-transition metal complexes have been combined in metallodendrimers to create the potential for a wide range of utilitarian applications. Because dendrimers allow scientists to probe the twilight zone between homogeneous and heterogeneous catalysis as well as to apply the techniques associated with combinatorial-type chemistry, diverse new areas of the nanoworld have became accessible. Since many new avenues in supramolecular chemistry have been opened by organometalhc complexes, metallodendrimers will continue to play an important role in not only organometalhc chemistry and polymer science, but also in material science. These new interfaces will be rich areas for future science to pursue. 

Personnel in the microbiology laboratory normally have the same safety concerns as those in the chemistry laboratory but, additionally, may face challenges unique to their workplace. These include the potential for unexpected exposure to billions of potentially pathogenic microorganisms, the use of high-pressure sterilization equipment, open flames for aseptic techniques, and extremely toxic media ingredients (e.g., cyclo-heximide, DMDC, etc.). 

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