Surface chirality

The polymers described so far have relatively flexible main chains which can result in complex confonnations. In some cases, tliey can double back and cross over tliemselves. There are also investigations on polymers which are constrained to remain in a confonnation corresponding, at least approximately, to a straight line, but which have amphiphilic properties tliat ensure tliat tliis line is parallel to tire water surface. Chiral molecules are one example and many polypeptides fall into tliis class [107]. Another example is cofacial phtlialocyanine polymers (figure C2.4.9). 

The ability of STM to image at the atomic scale is particularly exemplified by the two other chapters in the book. Thornton and Pang discuss the identification of point defects at Ti02 surfaces, a material that has played an important role in model catalyst studies to date. Point defects have been suggested to be responsible for much of the activity at oxide surfaces and the ability to identify these features and track their reactions with such species as oxygen and water represents a major advance in our ability to explore surface reactions. Meanwhile, Baddeley and Richardson concentrate on the effects of chirality at surfaces, and on the important field of surface chirality and its effects on adsorption, in a chapter that touches on one of the fundamental questions in the whole of science - the origins of life itself ... 

The modification of platinum-group metals by adsorbed chiral organic modifiers has emerged as an efficient method to make catalytic metal surfaces chiral. The method is used to prepare highly efficient catalysts for enantioselective hydrogenation of reactants with activated C = O and C = C groups. The adsorption mode of the chiral modifier is crucial for proper chiral modification of the active metal surfaces. The most efficient chiral modifiers known today are cinchona alkaloids, particularly CD, which yields more than 90% enantiomeric excess in the hydrogenation of various reactants. 

This contribution is restricted to supramolecular chiral phenomena on solid surfaces. Neither interaction of molecules with chiral inorganic surfaces [4], nor chiral amphiphilic molecules at the air-water interface are considered [5-8]. It is the intent of this review to present principle aspects of surface chirality. That is, examples are used to highlight typical chiral assembly mechanisms and structures. Most of these examples, however, belong to more than one aspect presented within this review. Hopefully, this set-up will be accessible to the reader who is not working with surfaces as well as informative to those who are familiar with the subject. 

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