Supramolecular supermolecule

According to these basic concepts, molecular recognition implies complementary lock-and-key type fit between molecules. The lock is the molecular receptor and the key is the substrate that is recognised and selected to give a defined receptor—substrate complex, a coordination compound or a supermolecule. Hence molecular recognition is one of the three main pillars, fixation, coordination, and recognition, that lay foundation of what is now called supramolecular chemistry (8—11). 

Paraphrasing Corey s historic definition of synthon [203], Desiraju defined a supramolecular synthon as a structural unit within a supermolecule that can be formed or assembled by known or conceivable synthetic operations involving intermolecular interactions [204], The robustness of the XB has allowed several supramolecular synthons based on this interaction to be identified and some examples have been presented in this chapter. 

Lehn JM. 1988. Supramolecular chemistry—Scope and perspectives molecules, supermolecules, and molecular devices. Angewandte Chemie—International Edition in English 27(1) 89-112. 

The tin(II) derivative Sn[S2P(OPh)2]2 is a dimeric supermolecule formed through intermolecular Sn- S secondary bonds and Sn-7i-aryl interactions.57 Lead(II) dithiophosphates, Pb[S2P(OR)2]2, e.g. R = Me,58 Pr" and Cy,59 all form supramolecular chain-like arrays. The ligands are unsymmetrically bridging and form Pb- S secondary bonds. 

The structural chemistry of some metal dithiocarbamates, i.e. systematics, coordination modes, crystal packing, and supramolecular self-assembly patterns of nickel, zinc, cadmium, mercury,363 organotin,364 and tellurium,365 366 complexes has been thoroughly analyzed and discussed in detail. Supramolecular self-assembly frequently occurs in non-transition heavier soft metal dithiocarbamates. Thus, lead(II),367 bismuth(III)368 zinc,369 cadmium,370 and (organo)mercury371 dithiocarbamates are associated through M- S secondary bonds, to form either dimeric supermolecules or chain-like supramolecular arrays. The arsenic(III)372 and antimony(III)373 dithiocarbamates are... 

For many chemists LCs are mysterious and complex materials, their very definition defying a simple understanding. The basic idea behind this discussion of stereochemistry in LCs is that molecules and LCs represent the same phenomenon. Liquid crystals are supermolecules in a different way than are supramolecular assemblies. Indeed, LCs can be composed of supramolecular... 

Liquid crystals are thermodynamic phases composed of a great many molecules. These molecules, termed mesogens, possess a free energy of formation, of course. LCs (their structure, properties, everything that gives them their unique identity), however, are not defined at the level of the constituent molecules any more than a molecule is defined at the level of its constituent atoms. LCs are supermolecules. How do they differ from supramolecular... 

The building blocks of supramolecular systems are held together by intramolecular interactions and these systems are reversible. This intrinsic property is not only a consequence of the more labile interactions within supermolecules, compared to covalent bonds in molecules, but reversibility is essential for the function expressed by supramolecular systems. Kinetics can never be inferred from thermodynamic studies. For example, the knowledge of a host-guest equilibrium constant does not... 

The progression from elementary particles to the nucleus, the atom, the molecule, the supermolecule and the supramolecular assembly represents steps up the ladder of complexity. Particles interact to form atoms, atoms to form molecules, molecules to form supermolecules and supramolecular assemblies, etc. At each level novel features appear that did not exist at a lower one. Thus a major line of development of chemistry is towards complex systems and the emergence of complexity. 

J. M. Lehn, Supramolecular chemistry—scope and perspectives. Molecules, supermolecules, and molecular devices, Angew. Chemie. Int. Ed. Engl. 27, 89-112(1988). 

Interactions can be combined by a designed placement of functional groups in the molecular skeleton to generate supramolecular synthons, which are defined as structural units within supermolecules that can be formed and/or assembled by known or conceivable synthetic operations involving intermolecular interactions (Desiraju, 1995). In other words supramolecular synthons are spatial arrangements of intermolecular interactions. 

The continued interest in dendritic materials as well as the related hyperbranched polymers has sparked the imagination of researchers in many different areas. The incredible increase in annual publications in this topic is best shown in the Figure and thus as the number on new building blocks and core molecules proliferate, the structural composition of precise and controlled design will grow to meet the imagination of molecular architects. This review series was initially conceived to cover the synthesis and supramolecular chemistry of dendritic or cascade supermolecules as well as their less perfect hyperbranched cousins. 

A secondary bond , as defined by Alcock [6-8], is an interaction between two atoms characterized by a distance longer than the sum of the covalent radii but shorter than the sum of the van der Waals radii of the corresponding atoms. Such secondary interactions are weaker than normal covalent or dative bonds, but strong enough to connect individual molecules and to modify the coordination geometry of the atoms involved. They are often present in a crystal, thus resulting in self-assembled supermolecules or supramolecular architectures. For gold complexes,... 

Finally, although much less frequent, there are also supramolecular gold materials formed as a result of the presence of different types of interactions in which n electron density is responsible for the formation of a supermolecule or a supramolecular array. Thus, Au- %, —H- % or % n interactions will also be considered in this chapter. 

Fig. 1. From molecular to supramolecular chemistry molecules, supermolecules, molecular and supramolecular devices.

One point to address concerns the use of the words s pramolecular and supermolecule. The concept of supramolecular chemistry has become a unifying attractor, in which areas that have developed independently have spontaneously found their place. The word supramolecular has been used in particular for large multiprotein architectures and organized molecular assemblies [1.16]. On the other hand, in theoretical chemistry, the computational procedure that treats molecular associations such as the water dimer as a single entity is termed the supermolecule approach [1.34,1.35]. Taking into account the existence and the independent uses of these two words, one may then propose that supramolecular chemistry be the broader term, concerning the chemistry of all types of supramolecular entities from the well-defined supermolecules to extended, more or less organized, polymolecular associations. The term super molecular chemistry would be restricted to the specific chemistry of the supermolecules themselves. 

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