Structure supramolecular architectures

The results presented up to here concern only one-dimensional oligomers and polymers of the PPP-lype. This section is mainly focussed on the electronic properties of extended re-chains and on the morphology of solid PPPs using chain-stiffness as a structure-forming principle for supramolecular architectures. 

Hawthorne and co-workers have also produced a series of macrocyclic Lewis acid hosts called mercuracarborands (156, 157, and 158) (Fig. 84) with structures incorporating electron-withdrawing icosahedral carboranes and electrophilic mercury centers. They were synthesized by a kinetic halide ion template effect that afforded tetrameric cycles or cyclic trimers in the presence or absence of halide ion templates, respectively.163 These complexes, which can bind a variety of electron-rich guests, are ideal for catalytic and ion-sensing applications, as well as for the assembly of supramolecular architectures. 

Many of the materials currently under development draw their inspiration from structures found in nature. That is, by mimicking the supramolecular architecture of natural materials, one can prepare complex materials capable of highly sophisticated functions. An important aspect of this work involves the selection of microorganism templates (e.g., diatomite) based on specific porous structures that may benefit targeted applications. 

Perhaps the common characteristic of all contributions to this volume is the permanent concern about the intimate relationships between the structural and electronic properties. Indeed, the careful design of increasingly complex molecular and supramolecular architectures allows us now to anticipate many molecular and solid state properties, but the final solid state structures are always the results of many competing interactions. The resulting electronic properties of these radical assemblies, whether conductivity or magnetism, are always very sensitive to minute modifications of their solid state structures and one of the main difficulties through... 

In Chapter 5, Spector, Selinger, and Schnur describe such supramolecular architectures, which are formed in water from compounds derived from natural materials that have been altered in their ability to pack. Chirality plays an essential role in this area. However, there are the questions as to why these supramolecular structures are formed, the answers to which can improve approaches to control their architectures and dimensions. These authors evaluate several theories proposed to answer these fundamental questions. 

C. A. Schalley, J. M. Rivera, T. Martin, J. Santamaria, G. Siuzdak, J. Rebek, Jr, Structure Determination of Supramolecular Architectures by Electrospray Ionization Mass Spectrometry , Eur. J. Org Chern., 1999, 1325-1331. 

A transition from ID- to 2D Jt-conjugated structures has important consequences for the n-electron structure.1131 Furthermore, it is challenging to investigate supramolecular architectures formed from disc-type structures. 

Supramolecular architectures in which transition metal cationic centres are linked via hydrogen-bonded supramolecular synthons [1,2] comprise an increasingly important class of inorganic co-ordination polymers [3], owing to their multi-dimensional, multi-functional network structures. 

The chemistry of metal complexes featuring alkyne and alkynyl (acetylide) ligands has been an area of immense interest for decades. Even the simplest examples of these, the mononuclear metal acetylide complexes L MC=CR, are now so numerous and the extent of their reaction chemistry is so diverse as to defy efforts at a comprehensive review. " The utility of these complexes is well documented. Some metal alkynyl complexes have been used as intermediates in preparative organic chemistry and together with derived polymeric materials, many have useful physical properties including liquid crystallinity and nonlinear optical behaviour. The structural properties of the M—C=C moiety have been used in the construction of remarkable supramolecular architectures based upon squares, boxes, and other geometries. ... 

The structures of several compounds with Au-Mn and Au-Re bonds have been reported and all are neutral or ionic species without further association through metal-metal interaction resulting in supramolecular architectures. 

Molecular organization and self-assembly into layers, membranes, vesicles etc., construction of multilayer films [7.1-7.5], generation of defined aggregate morphologies [4.74, 4.75, 7.6-7.8J etc., make it possible to build up specific supramolecular architectures. The polymerization of the molecular components has been a major step in increasing control over the structural properties of such assemblies [7.9-7.13]. 

Molecular devices have been defined as structurally organized and functionally integrated chemical systems they are based on specific components arranged in a suitable manner, and may be built into supramolecular architectures [1.7,1.9]. The function performed by a device results from the integration of the elementary operations executed by the components. One may speak of photonic, electronic or ionic devices depending on whether the components are respectively photoactive electroactive or ionoactive, i.e., whether they operate with (accept or donate) photons, electrons, or ions. This defines fields of molecular and supramolecular photonics, electronics and ionics. 

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.). 

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