Functional supermolecules

Two basic types of components may be distinguished active components, that perform a given operation (accept, donate, transfer) on photons, electrons, ions, etc. structural components, that participate in the build-up of the supramolecular architecture and in the positioning of the active components, in particular through recognition processes in addition, ancillary components may be introduced to modify or perturb the properties of the other two types of components. A basic feature is that the components and the devices that they constitute should perform their function ) at the molecular and supramolecular levels as distinct from the bulk material. Incorporation of molecular devices into supramolecular architectures yields functional supermolecules or assemblies (such as layers, films, membranes, etc.). 

Molecular Devices with Directional Functionality-Supermolecules That Transmit Signals in a Desired Direction The ability to direct the flow of information in a desired direction is crucial to molecular device development. Controlled organization of functional molecifles, mainly using the LB method, was used to prepare molecular devices regulating electron or energy flow. 

Molecular Devices with Directional Functionality-Supermolecules that Transmit Signals in a Desired Direction... 

Ariga et al. (2007) in a excellent review present, in a well documented and elegant way, the flexibility of the synthesis and formulation methods for designing and developing the mesoporous nanospaces, if the fundamental principles of supramolecular and coordination chemistry are taken as the leading concept. It was revealed that the structural dimensions of mesoporous materials permit access by functional supermolecules, including coordination complexes, and control of their functionality can be achieved by variation of pore geometry. 

The AB supermolecule is described by a single determinant wave function formulated in terms of doubly occupied molecular orbitals with no orthonormality constraints. For a system with 2N = 2Na +2Nb electrons the SCF-MI wave function expressed in terms of the antisymmetrizer operator A is... 

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 peculiar features of the three arAR supermolecules were translated into pharmacophore hypotheses by means of Catalyst software (Figure 8.2, unpublished results). Catalyst treats molecular structures as templates placing chemical functions in 3D space to interact with the receptor. Molecular flexibility is taken into account by considering each compound as a collection of conformers representing different areas of the molecules conformational space within a given energy range. 

The best statistical parameters were obtained by correlating the in vivo selectivity with the Vdif descriptor defined with respect to the oqa-AR supermolecule. It is worth noting that the oqa is the adrenergic receptor subtype of functional relevance for the urethra tissue (dog model) [8]. Thus, ligands showing high potency and selectivity for the lower urinary tract are those, which better fit the volume of the supermolecule that represents the binding site of the ala-AR subtype. 

Lehn, J. M. Supramolecular chemistry - Molecules, supermolecules, and molecular functional units. Angew. Chem. Int. Ed. Engl. 1988, 27, 89-112. 

Ab initio STO-3G calculationswere performed on the supermolecules formed by a nucleophile and a chiral substrate (2-chloropropanal or 2-methylbutanal). The nucleophile, simulated by H , is located at 1.5 A from the carbon atom, in a direction perpendicular to the carbonyl axis. Hence, to each reaction correspond two diastereoisomeric supermolecules resulting from attack on one face or the other of the 7T system. These molecules are thus models of the diastereoisomeric transition states. In Fig Ill and IV, their relative energies are plotted as a function of their conformations. The solid (dashed) lines correspond to the transition states of type 5... 

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. 

One case, however, where materialization of a specific solvent molecule out of the continuum is indeed critical is when that solvent molecule loses its solvent character. For instance, a water molecule tightly bound as both a hydrogen-bond donor and acceptor in a chain involving two solute functional groups clearly should be regarded as a unique fragment in what is fundamentally a two-piece supermolecule. Unfortunately, it is not always... 

Dynamic features of supermolecules correspond on the intermolecular level to the internal conformational motions present in molecules themselves and define molecular recognition processes by their dynamics in addition to their structural aspects. They add a further important facet to the behaviour of these species and may influence their functional features in reactions and transport processes as well as in polymolecular assemblies. 

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