Supramolecular aggregation

Chen S-FI, Fluang J S and Tartaglia P (eds) 1992 Structure and Dynamics of Strongly Interacting Colloids and Supramolecular Aggregates in Solution (Dordrecht Kluwer) pp 229-429... 

Fig. 7. Formation of a supramolecular aggregate composed of a compound containing nine melamine rings (the three-layered nonamelamine derivative A) and nine molecules of neohexylisocyanurate (B). Of the 16 possible conformers that can result, two are shown The first has the nine molecules of B arranged in three rosettes of three molecules each, stacked atop each other in the second, the rosettes are staggered with respect to each other such that the rosettes in the first and third layers of A are aligned with each other, but not with the rosette in the second layer. The supramolecular assembly is stabilized...

Static (multi-angle laser) light scattering (SLS or MALLs) Molecular weight, radius of gyration, Rg solution conformation and flexibility. Solutions need to be clear of supramolecular aggregates. Rg more sensitive to conformation than s. [3]... 

Supramolecular Aggregates, Also Termed Micro Reactors 19... 

Casas, J.M., Diosdado, B.E., Falvello, L.R., Fornies, J., Martin, A. and Rueda, A.J. (2004) Hydrogen-bond mediation of supramolecular aggregation in neutral bis-(C5F5)Pt complexes with aromatic H-bond donating ligands. A synthetic and structural study. Dalton Transactions, (17), 2733-2740. 

Vickery, J.C., Olmstead, M.M., Fung, E.Y. and Balch, A.L. (1997) Solvent-stimulated luminescence from the supramolecular aggregation of a trinuclear gold(I) complex that displays extensive intermolecular Au Au interactions. Angewandte Chemie, 109, 1227-1229 (1997) Angewandte Chemie (International Edition in English), 36, 1179-1181. 

Richter D (1992) In Chen SH et al. (eds) Structure and dynamics of strongly interacting colloids and supramolecular aggregates in solutions. Kluwer, Amsterdam, 111... 

Each of the examples (5.1)—(5.4) illustrates the linking of molecules into supramolecular species that constitute new units of liquid, gaseous, or solid phases. Other provocative examples of supramolecular aggregation include the al-lotropic phases of sulfur (composed of a variety of linear and cyclic polymeric chains)9 and the remarkable Zintl salts (with anions composed of variable metal clusters).10... 

Supramolecular aggregations are commonly referred to by a variety of terms, including adduct, complex, and van der Waals molecule. In this chapter we shall primarily employ the more neutral term cluster, which may, if desired, be qualified with the type of intermolecular interaction leading to clustering (e.g., H-bonded cluster ). General and specific types of intermolecular forces are discussed in the following sections. 

At shorter distances, particularly those characteristic of H-bonded and other charge-transfer complexes, the concepts of partial covalency, resonance, and chemical forces must be extended to intramolecular species. In such cases the distinction between, e.g., the covalent bond and the H-bond may become completely arbitrary. The concept of supramolecular clusters as fundamental chemical units presents challenges both to theory and to standard methods of structural characterization. Fortunately, the quantal theory of donor-acceptor interactions follows parallel lines for intramolecular and intermolecular cases, allowing seamless description of molecular and supramolecular bonding in a unified conceptual framework. In this sense, supramolecular aggregation under ambient thermal conditions should be considered a true chemical phenomenon. 

On the other hand, cellular membranes are composed of chiral molecules such as phospholipids and cholesterol, but the homochirality of these constituents is not obviously manifested in the membrane s structure. However, in certain cases biological membranes exhibit a distinct helical or twisted structure, which is a very conspicuous sign of the chirality of the supramolec-ular aggregate. These chiral supramolecular aggregates are the subject of this chapter. 

Metal phthalocyanines functionalized with four helicenes (62) have also been reported to form chiral columnar aggregates.76 In chloroform solutions of these metal phthalocyanines aggregation into columns occurred upon addition of ethanol, as was observed by UV-Vis spectroscopy. CD spectroscopy revealed that the chromophores within the columnar aggregates are in a chiral environment, implying that the chirality of the peripheral helicenes has been transferred to the supramolecular aggregates. These phthalocyanines stack with a typical intermolecular distance of 3.4 A, and calculations have indicated that to allow this distance the two phthalocyanine moieties have to be rotated because of the bulkiness of the helicenes. It can easily be imagined that a phthalocyanine provided with both R and S helicenes cannot stack in such a defined manner because of the steric interactions between the nonconform helicenes. 

Size and shape Certain steric effects can be achieved using characteristically wedge-shaped dendrons. Thus, self-assembling dendrons have been connected to supramolecular aggregates with defined dimeric or hexameric structures. Such aggregates can form columnar superstructures which reveal liquid-crystalline properties. Spherical superstructures arise from the self-assembly process when conical dendrons are used14 14,161 Similar... 

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