Templating metal

The synthesis of the Ni(n) complex of the 13-membered (anionic) macrocycle (78) is also achieved using an in situ procedure (Cummings Sievers, 1970) in which triethylenetetramine, acetic acid, acetylacetone, and nickel acetate are heated in water at the reflux. Addition of iodide ion and adjustment of the pH of the solution to approximately 10, leads to crystallization of the Ni(n) complex of the required cyclized product (78) as its iodide salt. The reaction type has been extended to include Cu(ii) as the template metal (Martin, Wei Cummings, 1972) and has also been... 

The ligand reaction step may occur either with the template metal still intact or may take place after removal of the metal ion from the ring. As already mentioned, many of the Schiff-base macrocycles are unstable in the absence of a coordinated metal ion. However, for such systems, it has often been possible to hydrogenate the coordinated imine functions directly. The resulting saturated ligands will not be subject to the hydrolytic degradation which occurs for the imine precursors in the absence of their metal ion. 

Manganese(II) has been commonly employed as a templating metal ion for the synthesis of a wide range of other mixed donor (oxygen/nitrogen) Schiff base macrocycles (and/or their imine-reduced derivatives). 

Czuryszkiewicz T, Rosenholm J, Kleitz F, Linden M (2002) Synthesis and characterization of mesoscopically ordered surfactant/cosurfactant templated metal oxides. Impact of Zeolites and Other Porous Materials on the New Technologies at the Beginning of the New Millennium, Book Series Studies in Surface Science and Catalysis, Pts A and B 142 1117-1124... 

We are developing a new method for preparing heterogeneous catalysts utilizing polyamidoamine (PAMAM) dendrimers to template metal nanoparticles. (1) In this study, generation 4 PAMAM dendrimers were used to template Pt or Au Dendrimer Encapsulated Nanoparticles (DENs) in solution. For Au nanoparticles prepared by this route, particle sizes and distributions are particularly small and narrow, with average sizes of 1.3 + 0.3 nm.(2) For Pt DENs, particle sizes were around 2 nm.(3) The DENs were deposited onto silica and Degussa P-25 titania, and conditions for dendrimer removal were examined. 

Template Polymers. Template effects in chelating polymers constitute an interesting development in the field of metal containing polymers. The Template effects are interpreted by the fact that the small molecule is templating a pattern in the macromolecule which can be recognized by the same molecule in a subsequent process. The idea is to prepare a polymer from the metal-chelated monomer, to remove the metal ion, and then to measure the selectivity of the prepared polymer for the metal ion of the template [36]. Typical examples of template systems are 4-vinyl-4 -methylbipyridine (Neckers [36]) and 1-vinyl-imidazole (Tsuchida [37]). These are polymerized in presence of divinylbenzene [36] and appropriate metal salts (Co2+, Cu2+, Ni2+, Zn2+). The template metal ions are removed by acid leaching and the polymer subsequently used for metal ion absorption studies (Fig. 16). 

Several syntheses of tetrabenzoporphyrin complexes make use of similar template strategies to those used in phthalocyanine synthesis, so they will be discussed here. An isoindole has been found to undergo a very complex series of reactions promoted by a range of metal ions in refluxing 1,2,4-trichlorobenzene to produce tetrabenzoporphyrin complexes (Scheme 55).240 In contrast, an extremely simple synthesis of tetrabenzoporphyrin can be achieved from 2-acetylbenzoic acid, using zinc as templating metal (equation 44).241... 

Template-metal coordinative bonds have also been used in the imprinting and recognition of carbohydrates in aqueous media. A MIP, templated with glucose and using 4-(iV-vinylbenzyl)diethylenetriamine)Cu(H)]diformate as... 

E tching/in sulator Template Metal or carbon fibre Carbon paste Recessed Conic Disk... 

In this system, however, intermolecular dimerization may take place competitively with intramolecular dimerization. To rule out this possibility, compound 5, in which two anthracenes are linked by two polyether chains, was synthesized.171 It was found that intramolecular photodimerization proceeds rapidly in the presence of Na+ as the template metal cation. Compound 6 was also synthesized.181 Although this compound has not been applied in a photoswitch system, it displays a remarkable fluorescence change upon binding with RbC104 or H3N+(CH2)7NHj.[81 Yama-shita et al.[9] also synthesized 7, in which intermolecular photodimerization of anthracene is completely suppressed. The photochemically produced cyclic form 8 displayed excellent Na+ selectivity. 

Fig. 4 The apparent pseudo-first-order rate constant /cobs (s ) for the formation of benzo-18-crown-6 as a function of the concentration of templating metal cation (M + = Li +, Na+, K +, Rb +, and Cs + ).53...

Brinker CJ Dunphy DR, Morphological control of surfactant-templated metal oxide films, Curr. Opin. Colloid Interface Set, 2006, 11, 126-132. 

Organically-templated metal sulfates, selenites and selenates... 

The literature on inorganic open-framework materials abounds in the synthesis and characterization of metal silicates, phosphates and carboxylates. Most of these materials have an organic amine as the template. In the last few years, it has been shown that anions such as sulfate, selenite and selenate can also be employed to obtain organically templated open-framework materials. This tutorial review provides an up-to-date survey of organically templated metal sulfates, selenites and selenates, prepared under hydrothermal conditions. The discussion includes one-, two-, and three-dimensional structures of these materials, many of which possess open architectures, The article should be useful to practitioners of inorganic and materials chemistry, besides students and teachers. The article serves to demonstrate how most oxy-anions can be used to build complex structures with metal-oxygen polyhedra. 

An effective template metal ion binds strongly to the donor atoms of the macrocycle or its precursors, e.g., K+ is the most common template for synthesis of crown ethers and forms definite complexes with a wide variety of crown ethers. 

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