Molecular/supramolecular templating

Since the discovery of the M41S materials with regular mesopore structure by Mobils scientists [1], many researchers have reported on the synthetic method, characterization, and formation mechanism. Especially, the new concept of supramolecular templating of molecular aggregates of surfactants, proposed as a key step in the formation mechanism of these materials, has expanded the possibility of the formation of various mesoporous structures and gives us new synthetic tools to engineer porous materials [2],... 

The synthesis of molecular sieves with large pores is of great importance for many applications such as catalysis, separation, adsorption and fabrication of various quantum materials [1-7]. With the recent discovery of hexagonal and cubic large pore mesoporous materials (SBA-15, SBA-16, FDU-1) [2,3], block copolymers have turned out to be valuable supramolecular templates for the synthesis of ordered large pore mesoporous materials because of their facile structure-directing ability, low-cost commercial availability and biodegradability. 

Ozin and coworkers recently extended the supra-molecular I S+ assembly into the synthesis of binary mesoporous yttrium oxide-stabilized-zirconium oxide materials.These materials were synthesized by a modified sol-gel method under basic conditions, where zirconium ethoxide and yttrium acetate were used as the precursors for the transition metal oxides, and CTAB was used to form the supramolecular templates. The use of ethylene glycol with coordinating capability as a cosolvent may play a role in controlling the hydrolysis rate and solubility of zirconium(IV) and yttrium(III). This synthesis strategy is similar to that of so-called polymerizable-complex method, which was widely used to prepare multicomponent single-phase oxides. The yttrium content in these binary materials can be tuned from 12-56 wt%, and no phase segregation of yttrium and zirconium oxides was observed. These materials could be applied in designing new solid oxide fuel-cell electrode materials. 

As described above, molecular and supramolecular templating methods have been very successfully applied for the syntheses of a large variety of microporous systems (e.g., zeolites, AlPOs) and mesoporous systems, respectively. Such approaches allow the design of the pore structure inside a crystal or particle. The simultaneous control about the pore structure at the micro and the macro scale during the formation process can be realized by the combination of at least two strategies. The combination of molecular templating with a sol-gel processing approach results in porous spheres [204]. 

Multimodal porous systems in the form of monolithic-shaped forms (bodies) were obtained from a process where a (true) liquid-crystal templating is combined with a sol-gel process [205]. One characteristic of such a process is the incompatibility of lyotropic surfactants with an alcohol, mostly an inherently produced alcohol, which is responsible for the phase separation during the sol-gel processing, stabilizing the resulting monolithic architecture of the monolith [206]. Different approaches use various components, namely, the alcohol source, the silicate sources (both are sometimes combined in one molecule), and molecular or supramolecular templating agents [207]. 

Chen Z, Li Z, Guo H, Zhang J, Ren Z, Yan S, Xie P, Zhang R (2012) Supramolecular template-directed synthesis of soluble quadruple-chain ladder polyphenylsiloxane (Ph-QCLP) with high molecular weight. Chem Mater 24(10) 1968-1973. doi 10.1021/ cm300951x... 

The use of ordered supramolecular assemblies, such as micelles, monolayers, vesicles, inverted micelles, and lyotropic liquid crystalline systems, allows for the controlled nucleation of inorganic materials on molecular templates with well-defined structure and surface chemistry. Poly(propyleneimine) dendrimers modified with long aliphatic chains are a new class of amphiphiles which display a variety of aggregation states due to their conformational flexibility [38]. In the presence of octadecylamine, poly(propyleneimine) dendrimers modified with long alkyl chains self-assemble to form remarkably rigid and well-defined aggregates. When the aggregate dispersion was injected into a supersaturated... 

Sauvage, J.-P. Dietrich-Buchecker, C. O. Chambron, J.-C. Transition metals as assembling and templating species synthesis of catenanes and molecular knots. In Comprehensive Supramolecular Chemistry, Sauvage, J.-P. Hosseini, M.W., Ed., Publisher Elsevier, Oxford, UK 1996 Vol. 2, p 43. 

Currently the main interest in template reactions lies in their key role in the controlled synthesis or the self-assembly of a variety of supramole-cular entities (449). One needs a combination of intuition, conjecture, and serendipity (450) a recent example of successfully combining serendipity and rational design is provided by the silver(I)-promoted assembly of one-dimensional stranded chains (451). One also needs an understanding of mechanism in order to optimize the selection and design of building blocks and templates for the generation of yet more sophisticated supramolecular structures references cited in this present review contain at least some kinetic or mechanistic information or speculation. Template routes to interlocked molecular structures have been reviewed (452), while a discussion of switching by transition metal contains a little about the kinetics and mechanisms of this aspect of template... 

Very recently, MacGillivray et al. succeeded in the supramolecular construction of molecular ladders in the solid state using a linear template approach [48]. They designed the cocrystals 1,3-benzenediol (resorcinol) or a derivative with an all-trans-bis(4-pyridyl)butadiene or hexatriene, in which two resorcinol molecules preorganize two polyene molecules through two hydrogen bond interactions, for [2-1-2] photoaddition (Scheme 5). In this design, two polyenes would... 

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