Polymolecular associations

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. 

Gouy distorted square planar coordination suggested possibly polymolecular association by intermolecular hydrogen bonding 74A20... 

Continuous progress is being made in the design of synthetic molecular assemblies, based on a growing understanding of the relations between the properties of the molecular components (structure, sites for intermolecular binding, polar-apo-lar domains, etc.), the characteristics of the processes that lead to their association and the supramolecular features of the resulting polymolecular entity. 

It is reasonable to assume that the complementary units form the expected triply hydrogen bonded pairs, so that the entirely different behaviour of the pure compounds and of the 1 1 mixtures may be attributed to the spontaneous association of the complementary components into a polymolecular entity based on hydrogen bonding. The overall process may then be described as the self-assembly of a supramolecular liquid-crystalline polymer based on molecular recognition (Figure 40). The resulting species (TP2, TU2) is represented schematically by structure 174. 

There are two types of objects in supramolecular chemistry supermolecules (i.e., well-defined discrete oligomolecular species that result from the inter-molecular association of a few components), and supramolecular arrays (i.e., polymolecular entities that result from the spontaneous association of a large, undefined number of components) (4, 5). Both are observed in some metal-xanthate structures to be described herein. The most frequent intermolecular forces leading to self-assembly in metal xanthates are so-called secondary bonds . The secondary bond concept has been introduced by Nathaniel W. Alcock to describe interactions between molecules that result in interatomic distances longer than covalent bonds and shorter than the sum of van der Waals radii (6). Secondary bonds [sometimes called soft-soft interactions (7)] are typical for heavier p-block elements and play an important role as bonding motifs in supramolecular organometallic chemistry (8). Other types of intermolecular forces (e.g., Ji- -ji stacking) are also observed in the crystal structures of metal xanthates. 

There are two types of subjects in supramolecular chemistry (a) the supramolecular assemblies or systems, also called supramolecular arrays, that is, polymolecular entities that resultfrom the spontaneous association of a large undefined number of components, and (b) supermolecules, that is, well-defined discrete oligomolecular species that result from the intermolecular association of a few components... 

In another study, Selb and Gallot investigated the conformational properties of poly(styrene-g-4-vinyl-N-ethylpyridinium bromide) in water/methanol/LiBr mixtures [306]. The graft copolymers did not show intermolecular association in contrast to the linear block copolymers. Viscometric results showed that these graft copolymers also form compact, star-like monomolecular micelles with polystyrene cores and poly(4-vinyl-V-ethylpyridinium bromide) coronas, which resemble the polymolecular micelles of diblock materials. 

Consequently, the polydispersity Mn)w (MN)n for segment-related association as well as for molecule-related association is always smaller than the polymolecularity M )w j M )n. linear relationship between these two quantities exists for molecule-related, but not segment-related, association ... 

Though the polymolecularity of such molecular associations perhaps might remind one phenomenologically of the particles of hydrophobic sols, from the thermo-... 

Various polymethine dyes (pinacyanol, pseudoisocyanine) are soluble in alcohol and acetone as well as water. In the first two solvents the spectrum does not change as the concentration is raised in these cases the dyes follow Beer s law. On the other hand if the solvent is water, important modifications take place in the spectrum (ScHEiBE et al ). These changes which are associated with a great rise of the viscosity, can best be explained by an association of the ions of the dye, first to double ions, later to polymolecular formations. 

Supramolecular assembly Polymolecular entities that result from the association of a large, undefined number of molecular entities into a specific phase having a definable organization., e.g. micelles, vesicles etc. 

At the same time, current implementations of NLDFT have a significant drawback theoretical adsorption isotherms in the region of polymolecular adsorption exhibit multiple steps associated with layering transitions. Experimentally, stepwise layering transitions are observed only for fluids confined to very smooth surfaces, such as mica... 

---