Template agents

Low temperature sol-gel technology is promising approach for preparation of modified with organic molecules silica (SG) thin films. Such films are perspective as sensitive elements of optical sensors. Incorporation of polyelectrolytes into SG sol gives the possibility to obtain composite films with ion-exchange properties. The addition of non-ionic surfactants as template agents into SG sol results formation of ordered mechanically stable materials with tunable pore size. 

One of the most successful approaches to the synthesis of metalla-supramolecular systems has been by templated self-assembly processes. Most of the templating agents used by synthetic chemists are either cationic or neutral species. Anions, on the other hand, have only fairly recently been successfully utilized as templates. The new metalla-macrocycles [Pd2Ni2(atu)4(PPh3)4X]3+ (atu = deprotonated amidinothiourea, X = C1, Br, I) have been prepared using anion templated syntheses. Only in the presence of each of these three halides are the metalla-macrocycles... 

Aza macrocycles have also been used as templating agents in the formation of zinc and other metal cation-containing aluminophosphates via hydrothermal synthesis.705 The zeolite-like structures have been formed in the presence of cyclam- and hexaaza-based macrocycles. 

Since Pedersen s original work on the use of cations to template the formation of crown ethers [18-20], a large number of different templating agents for macro-cyclization reactions have been reported. While the initial work concentrated on the use of metal cations, further developments demonstrated that species with hydrogen bonding donor or acceptor properties could be equally useful to template the synthesis of macrocyclic molecules. 

Stoddart and Williams have reported the syntheses of a series of pseudoro-taxanes where the templating agent employed (an anion), although part of the... 

This selectivity can be attributed to the presence of the templating agent which, by hydrogen bonding, pre-organises the olefins before irradiation. 

The microporous sulfides are synthesized hydrothermally in the presence of alkylammonium templating agents. The GeS4-based composihons include one or more framework-incorporated metals Mn, Fe, Co, Ni, Cu, Zn, Cd and Ga. Over a dozen novel shuctures were reported which have no analogs in the microporous oxides. Ozin et al. have extended this work to a large number of microporous sulfides and selerhdes [53]. It should be noted that the microporous sulfides and selenides are prone to shucture collapse upon calcinahon to remove the template species. 

AIPO4-5 molecular sieve (BET surface area, 299 m g ) used in this study was prepared by the method of Wilson et al. [1j. VjOg/AIPO -S samples were prepared by impregnating with aqueous solutions of ammonium vanadate after removing templating agent in the AIPO -S by calcining at 530°C. The samples were dried at 110 C for 24 h then calcined in air at 550°C for 2 h. VAPO -S was prepared from gel mixture of phosphoric acid, pseudoboehmite, vanadium pentoxide, tri-propylamine and water (1.3 PrjN x AljOj PjOj 40 HjO) by crystallization at 165°C for 3 - 7 days [7. ... 

Figure 1. X-ray patterns of calcined MSU-1 and -4 Silica obtained with Tergitol 15S12 and Tween 20 as templating agents. The patterns were recorded with a Bruker D5000 diffractometer in Bragg-Brentano reflection geometry. Cu-L radiation was employed that was monochromatized by a graphite single crystal in the diffracted beam.

Poly(oxyethylene) oleyl ethers as templating agents for the synthesis of large pore mesoporous materials... 

Polyoxyethylene alkyl ether and in particular decaoxyethylene oleyl ether CigHj5 (CH2CH20)io can be used as templating agent for silica mesoporous materials formation. The synthesis can be performed under both acidic or basic conditions with tetramethoxysilane (TMOS) as silica source while no mesoporous compound was obtained with sodium silicate. 

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