Transition metals heavy

Rosen, B.P. 2002. Transport and detoxification systems for transition metals, heavy metals and metalloids in eukaryotic and prokaryotic microbes. Comparative Biochemistry and Physiology—A Molecular and Integrative Physiology, 133 689-93. 

The nitrogen atom of a Schiff base or oxime can coordinate to various metal ions (alkali metal, alkaline earth metal, transition metal, heavy metal ion). In particular, chelates such as salen (bis(salicylidene)ethylenediamine), saloph (bis(salicylidene)-o-phenylenediamine), and salamo (bis(salicylideneaminooxy)ethane) afford stable metal complexes, which are utilized for a variety of molecular functions such as catalysis of organic reactions, magnetism, luminescence, etc. °... 

Some of the basis sets discussed here are used more often than others. The STO—3G set is the most widely used minimal basis set. The Pople sets, particularly, 3—21G, 6—31G, and 6—311G, with the extra functions described previously are widely used for quantitative results, particularly for organic molecules. The correlation consistent sets have been most widely used in recent years for high-accuracy calculations. The CBS and G2 methods are becoming popular for very-high-accuracy results. The Wachters and Hay sets are popular for transition metals. The core potential sets, particularly Hay-Wadt, LANL2DZ, Dolg, and SBKJC, are used for heavy elements, Rb and heavier. 

The methods listed thus far can be used for the reliable prediction of NMR chemical shifts for small organic compounds in the gas phase, which are often reasonably close to the liquid-phase results. Heavy elements, such as transition metals and lanthanides, present a much more dilficult problem. Mass defect and spin-coupling terms have been found to be significant for the description of the NMR shielding tensors for these elements. Since NMR is a nuclear effect, core potentials should not be used. 

Transition-Metal and Other Heavy-Metal Fluoroborates... 

Manufacture. The transition- and heavy-metal fluoroborates can be made from the metal, metal oxide, hydroxide, or carbonate with fluoroboric acid. Because of the difficulty ia isolating pure crystalline soflds, these fluoroborates are usually available as 40—50% solutions, M(BP. Most... 

Propane, 1-propanol, and heavy ends (the last are made by aldol condensation) are minor by-products of the hydroformylation step. A number of transition-metal carbonyls (qv), eg, Co, Fe, Ni, Rh, and Ir, have been used to cataly2e the oxo reaction, but cobalt and rhodium are the only economically practical choices. In the United States, Texas Eastman, Union Carbide, and Hoechst Celanese make 1-propanol by oxo technology (11). Texas Eastman, which had used conventional cobalt oxo technology with an HCo(CO)4 catalyst, switched to a phosphine-modified Rh catalyst ia 1989 (11) (see Oxo process). In Europe, 1-propanol is made by Hoechst AG and BASE AG (12). 

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

Calculations [104] show that for L7 > A (the heavier transition metal ions) the gap is of the charge-transfer type, whereas for 1/ < A (the lighter transition metal ions) the gap is of the d-d type. In our nomenclature this may be translated as MMCT LMCT. In the charge-transfer semiconductors the holes are light (anion valence band) and the electrons are heavy (d bands). Examples are CuClj, CuBrj, CuO, NiClj, NiBrj and Nil2. 

The newly synthesized heavy analogs of the 67r-electron compounds have found a very promising application as ligands for a new generation of transition metal... 

Apart from d- and 4f-based magnetic systems, the physical properties of actinides can be classified to be intermediate between the lanthanides and d-electron metals. 5f-electron states form bands whose width lies in between those of d- and 4f-electron states. On the other hand, the spin-orbit interaction increases as a function of atomic number and is the largest for actinides. Therefore, one can see direct similarity between the light actinides, up to plutonium, and the transition metals on one side, and the heavy actinides and 4f elements on the other side. In general, the presence or absence of magnetic order in actinides depends on the shortest distance between 5f atoms (Hill limit). 

High sulfur content heavy crude oil may be recovered more efficiently using transition metal ions such as Ti or V and optionally carbon monoxide as steam additives (423). 

Layer silicate minerals have a high selectivity of trace transition and heavy metals and greater irreversibility of their adsorption. Some chemisorbing sites such as -SiOH or AlOH groups may be at clay edges and form hydroxyl polymers at the mineral surface. Another possible reason for the high selectivity may be hydrolysis of the metal and strong adsorption of the hydrolysis ion species. 

Both organic and inorganic ligands such as Cl and dissolved organic carbon (fulvie acid and carboxylic acids) decrease metal adsorption. In the arid soils with higher pH, folic acids increase the solubility of metals such as Cu and Zn. The interaction between the transition of heavy metals and silicate surfaces was reviewed by McBride (1991). 

Kinniburgh D.G., Jackson M.L., Syers J.K. Adsorption of alkaline earth, transition and heavy metal cations by hydrous gels of iron and aluminium. Soil Sci Soc Am J 1976 40 796-799. 

McBride M.B. Processes of heavy and transition metal sorption by soil mineral. In Interactions at the Soil Colloid-Soil Solution Interface, G.H. Bolt, M.F. De Boodt, M.H.B.Hayes, M.B. McBride, eds. NATO ASI Series (Series E Applied Sciences-Vol 190). Dordrecht, Netherlands Kluwer Academic Publishers, 1991. 

In the last example, a serious handicap is the extreme sensitivity of the calculations to the parameterization of the metal atoms. In a paper concerning the spin states of metal dimer complexes (38) as studied by EHT, heavy manipulation of the original theory was needed. In the field of transition metal coordination compounds self-consistent charge (SCC) calculations (of the type already mentioned for electronegative atoms) are essential to obtain the diagonal elements Hu. 

For the photodiagnostic use of these compounds, a high quantum yield of fluorescence, r, is desirable. The metal complexes of the common first-row transition metals are not suitable, because they show very low 4>f values. On the other hand, porphyrin complexes of d° and d10 elements show appreciable fluorescence, although generally less than that of the metal-free compounds, presumably because of the heavy-atom effect (e.g., TPP ZnTPP, Table 5). The further operation of the heavy-atom effect, which increases the rate of intersystem crossing (/cisc) by... 

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