Active functional material

Perfluorinated polyethers have also gained importance as actively functional materials. Ionic polymer membranes (e.g. DuPont s Nafion ) based on sulfonic acid-derivatized perfluoropolyethers have been used for nearly 30 years as ion-con-ducting membranes in chloralkali electrolysis cells, replacing the large amounts of toxic mercury used until then in the classic Castner-Kellner cells (Scheme 4.8.). One of the earliest applications of Nafion was as a membrane in the hydrogen-oxygen fuel cells which powered the Apollo spacecraft carrying the first men to the moon. 

If the adaptronic structure requires temperature stability, active functional materials must be used since they can have a flat temperature response away from the phase transition and are controllable with external fields. Most materials in this category are ferroic materials, i. e., ferroelectric, ferromagnetic and ferroelastic materials. 

Besides current development of new catalysts and related functional materials, oxidation tools have always played an important role in their synthesis, activation, and functionalization. After a separate discussion per technique we have rationalized our literature findings (Table 6.2) as five principal oxidative functions with many proven applications. 

In this brief review we illustrated on selected examples how combinatorial computational chemistry based on first principles quantum theory has made tremendous impact on the development of a variety of new materials including catalysts, semiconductors, ceramics, polymers, functional materials, etc. Since the advent of modem computing resources, first principles calculations were employed to clarify the properties of homogeneous catalysts, bulk solids and surfaces, molecular, cluster or periodic models of active sites. Via dynamic mutual interplay between theory and advanced applications both areas profit and develop towards industrial innovations. Thus combinatorial chemistry and modem technology are inevitably intercoimected in the new era opened by entering 21 century and new millennium. 

The difficulty is that characterization techniques are usually not selective towards active sites, so very often the main spectroscopic features are not evidence for active sites manifestations. However, it is possible to find some exceptions mainly among functionalized materials, such as zeolites. One of the few well established examples is TS-1 [7], a zeolite discovered in 1983 behaving as a catalyst for partial oxidation reactions in H2O2/H2O solutions [8-20]. 

Attempts to achieve selective oxidations of hydrocarbons or other compounds when the desired site of attack is remote from an activating functional group are faced with several difficulties. With powerful transition-metal oxidants, the initial oxidation products are almost always more susceptible to oxidation than the starting material. When a hydrocarbon is oxidized, it is likely to be oxidized to a carboxylic acid, with chain cleavage by successive oxidation of alcohol and carbonyl intermediates. There are a few circumstances under which oxidations of hydrocarbons can be synthetically useful processes. One group involves catalytic industrial processes. Much effort has been expended on the development of selective catalytic oxidation processes and several have economic importance. We focus on several reactions that are used on a laboratory scale. 

Martinez-Ferrero, E., Sakatani, Y., Boissire, C., Grosso, D., Fuertes, A., Fraxedas, J., and Sanchez, C. (2007) Nanostructured titanium oxynitride porous thin films as efficient visible-active photocatalysts. Advanced Functional Materials, 17 (16), 3348—3354. 

Jin, L., Xu, L., Morein, C., Chen, C., Lai, M., Dharmarathna, S., Dobley, A. and Suib, S.L. (2010) Titanium containing y-Mn02 (TM) hollow spheres one-step synthesis and catalytic activities in Li/air batteries and oxidative chemical reactions. Advanced Functional Materials, 20, 3373-3382. 

Commonly used material classes are the III-V compounds (especially when dynamic or active functions are needed), LiNbCh (because of its electro-optical properties), the indiffused glasses, the SiON-materials, the polymers and materials obtained from sol-gel technology. Last three will be treated in other chapters of this book. As an example we show the cross section of a simple channel structure based on SiON technology in Figure 6. 

The recent progress surveyed in this review shows the promise that late transition metal catalysts can provide in the production of new materials. We will continue our exploration of new catalyst design for the synthesis of new functional materials with unconventional topologies. Given the unique features of late transition-metal polymerization catalysts and further improvement in catalyst stability and activity for copolymerization with polar comonomers, the future of designing novel functional polymeric materials with late-transition-metal catalysts is very promising. 

Although the activation and functionalization of C-H bonds of alkanes are the important, promising routes for synthesis of functionalized materials, it is difficult to achieve the functionalization of alkanes because they are unreactive due to the low reactivity of alkane C-H bonds. Carboxylation of alkanes to carboxylic acids is one of the interesting and important functionalization processes. 

Synthetic reactions via C-H bond activation have been applied to the synthesis of natural products and the related molecules, development of functional materials, and functionalization of polymers. 

A large number of synthetic reactions via C-H bond activation have been reported in the last 10 years. In near future, applications to natural products and functional materials will be the next research targets, together with the development of new synthetic reactions. 

As already mentioned, the most important industrial application of homogeneous hydrogenation catalysts is for the enantioselective synthesis of chiral compounds. Today, not only pharmaceuticals and vitamins [3], agrochemicals [4], flavors and fragrances [5] but also functional materials [6, 7] are increasingly produced as enantiomerically pure compounds. The reason for this development is the often superior performance of the pure enantiomers and/or that regulations demand the evaluation of both enantiomers of a biologically active compound before its approval. This trend has made the economical enantioselective synthesis of chiral performance chemicals a very important topic. 

Tao et al. reported a series of light-emitting peripheral diarylamine derivatives containing carbazole units, which possess dual functions, as both active emitting materials and HTMs (Scheme 3.12) [79]. These luminescent materials are amorphous, with high Ts (120-194°C),... 

P-Amino carbonyl compounds containing an a-atkyUdene group are densely functionalized materials, which are widely applied in the synthesis of medicinal reagents and natural products [265]. These products are usually prepared through the classic aza-Morita-Baylis-Hillman reaction [176, 177] of activated imines and electron-deficient alkenes catalyzed by tertiary amines or phosphines. Chen and co-workers, in 2008, identified bis-thiourea 106 as a suitable catalyst for the... 

Lehn and coworkers also discussed the principles of design of self-assembling helical structures on the basis of conformational control. Depending on the solvent used, they were able to obtain helicate fibers and bundles possessing extended molecular channels characterized by hollow cores of limited diameter ofca. 8 A. This finding could form the basis of functional materials for multichannel ion active transport [28]. 

The biotransformation of organofluorine materials into optically active functionalized fluo-rinated materials along with a discussion on the effect of fluorine atom(s) during enantio-selective and/or diastereoselective transformations is described. The ability of microorganisms to discriminate between enantiomers is particularly important regarding resolution and asymmetric synthesis. Furthermore, the use of chiral fluorinated materials in the design and preparation of new types of biologically active materials is discussed. 

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