Supra molecular levels

Working at the atomic, molecular, supra-molecular levels, in the length scale of approximately 1—100 nm range, in order to understand, create and use materials, devices and systems with fundamentally new properties and functions because of their small structure. ... 

As regulation systems involving effectors, coupled transfers of charges and of mass, gates and pumps, transport processes extend towards the chemistry of information storage and retrieval at the molecular level, and are a major component in the design of molecular ionic devices (see Section 8.4). They thus open wide perspectives for the basic and applied developments of the functional features of supra-molecular chemistry. 

Fig. 46. Genealogy (information transfer) defined as a function of molecular supra-molecular, microscopic and macroscopic level entities found in biological systems. Vertical columns list various genealogical components involved throughout this hierarchy...

The most simple molecular topology of such systems reported so far is a tetrahedral supermolecule obtained by reacting tetrakis(dimethylsiloxy)-silane with alkenyloxy-cyanobiphenyls (Fig. 22), as discussed previously. Such tetramers exhibit smectic A liquid crystal phases [179]. For such end-on materials, microsegregation at the molecular level favors the formation of the smectic A phases in preference to the nematic phase exhibited by the mesogenic monomers themselves. The use of different polyhedral silox-ane systems (Fig. 24) or the Ceo polyhedron as the template for multi- and polypedal hexakis(methano)fullerenes (Fig. 70) substituted with a large number of terminally attached mesogenic groups confirm the same tendency to the formation of smectic A phases (vide supra). 

Much better than physicists, chemists are in an ideal position to develop bottom-up strategies towards the design of molecular-level machines, since they are able to manipulate molecules, i.e., the smallest entities of matter that have distinct shapes and properties. Forty years ago, however, the chemical community was not ready to receive Feynman s stimulation. Only recently, after the development of supra-molecular chemistry [1], has the study of artiflcial molecular-level machines become an important research topic in chemistry [15, 26-28, 33]. 

During the last two decades, there has been an enormous increase in the use of photophysical methods in supra-molecular chemistry. Until recently, photophysical methods, such as transient spectrometry and time-resolved fluorescence spectrometry, were primarily research tools in the arenas of photokinetics of small molecules, materials physics, and biophysics. This situation changed dramatically with the introduction of commercial, user-friendly electro-optical components such as charge-coupled detector (ED)-based spectrometers, solid-state pulsed lasers, and other instrumentation necessary for time-resolved measurements. As a result, time-resolved spectrometry became more available to the community of supramolecular chemists, who now reached the level of sophistication that can benefit from the new horizons offered. 

In this review, we have shown how computational chemistry can be used to successfully predict the important effects the environment has on properties and processes of (supra)molecular systems. The overview of the theoretical methods and the computational tools available is necessarily not exhaustive. However, those selected exemplify the most reliable and accurate protocols available for a correct comparison with the experiments. All of them are based on a multiscale strategy, where the whole system is partitioned into distinct but interacting parts, described at different levels of accuracy. Here, in particular, we have mostly focused on those multiscale strategies which combine a quantum chemical description with classical models. These strategies have shown to be extremely effective both in terms of the ratio of computational cost to accuracy, and their extensibility to systems of increasing complexity. We believe that these hybrid QM/classical approaches will continue to play a dominant role, even if the incredibly fast developments in the QM methods on one side and in the computational tools on the other side are rapidly extending the dimension of the QM part of the systems towards a reahsm which has never been reached before. 

In comparison to single-component films, bipolar semiconducting blends are much more challenging. The necessity to have percolation networks for both electrons and holes, each one conducted by one component of the blend, imposes strict requirements for the supra-molecular organization of the two materials. On one side an extended intermixing of the two semiconductors at the molecular level will... 

Furthermore, we predict that the dendritic state [312] will undoubtedly provide the quintessential scientific bridge by which both abiotic molecular level scientists will be able to communicate and collaborate on such critical issues as disease control, increased agricultural production and finally longevity with enhanced quality of life. It is with these thoughts and premises that we should be very excited about the future of dendritic macromolecular technology and the role its supra-properties will provide as we enter the next millennium. 

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