Supramolecular chemistry defined

Jean-Marie Lehn introduction of the term supramolecular chemistry , defined as the chemistry of... 

Jean-Marie Lehn Introduction of the term "Supramolecular Chemistry" defined as the. . chemistry of molecular assemblies... 

Since the coining of the term supramolecular chemistry - defined as the chemistry of molecular assemblies and of the intermolecular bond by Lehn in 1978 - supramolecular chemistry has undergone a spectacular expansion. A wide variety of chemical systems have been developed, which, although different in nature to the former systems, currently are also considered as real supramolecular ensembles. One of most remarkable examples is the field of supramolecular photochemistry, where, in a broader sense, a supramolecular compound is defined as a group of molecular components that contribute properties, which each component possesses individually, to the whole assembly. 

A rich domain emerges from the combination of polymer chemistry with supramolecular chemistry, defining a supramolecular polymer chemistry [23, 24]. It involves the designed manipulation of molecular interactions (hydrogen bonding, donor-acceptor effects, etc.) and recognition processes to generate main-chain (or side-chain)... 

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). 

Analytical chemistry having an interdisciplinary character cannot set aside the attractive power and advances of supramolecular chemistry - the chemistry beyond the molecule or the chemistry of molecular assemblies and of intermolecular bonds as defined by Jean-Marie Lehn, who won the Nobel Prize in 1987. Recognition, reactivity, and transport, as well as self-assembly, self-organization and self-replication are the basic functional features of supramolecular species and chemistry. 

This is a very new field, but given the current interest in both dendrimer chemistry and supramolecular chemistry, it is one that is likely to receive attention in the future. The prospect of preparing well-defined molecular assemblies, rather than ill-defined clusters, is attractive, and is expected to give access to new properties that can be controlled by the molecular architecture of the assembly. New and useful materials seem likely to emerge as this chemistry grows and is exploited in the years to come. 

The synthesis of the macrocycles 43 (Scheme 9) is an example of repetitive, highly stereoselective Diels-Alder reaction between bis-dienes 41 and bis-dienophiles 42, containing all oxo or methano bridges syn to one another. The consecutive inter- and intramolecular Diels-Alder reactions only succeed at high pressure. Obviously, both reactions are accelerated by pressure. The macrocycles are of interest in supramolecular chemistry (host-guest chemistry) because of their well-defined cavities with different sizes depending on the arene spacer-units. 

The concept and the term of supramolecular chemistry were introduced in 1978 [1.29] (see also [2.17]) as a development and generalization of earlier work in which the seed had been planted [1.27, 1.30]. It was defined in words, Just as there is a field of molecular chemistry based on the covalent bond, there is a field of supramolecular chemistry, the chemistry of molecular assemblies and of the intermolecu-lar bond , as well as in diagrammatic fashion (Fig. 1) [1.29]. 

It has since then been reformulated on various occasions, e.g., Supramolecular chemistry may be defined as chemistry beyond the molecule , bearing on the organized entities of higher complexity that result from the association of two or more chemical species held together by intermolecular forces [1.7]. 

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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