Host-guest properties introduction

Wheel-and-axle organic diols are host systems well known in the solid state. The introduction of a metal into the wheel-and-axle molecular frame opens the way for the design of materials with multiple functions, joining chemical and structural properties of the metal centre with the steric and supramolecular attitudes of the organic matrix. This chapter treats the rationalization of host-guest properties of wheel-and-axle inorganic diols. 

Following on from the introduction of the Kohn-Sham DFT concept came Runge and Gross DFT for time-dependent systems.Here the properties of molecules are determined as a snapshot in time and, consequently, can be modeled along a timeline to predict the evolution of a chemical species or reaction. The application of such a method to model supramolecular host-guest interactions and other complex phenomena, such as light-harvesting supramolecular complexes, is clear. 

Dendrimers and dendrons are appealing types of nanoscale, highly branched, macromolecules, which, because of their structure and properties, have attracted the interest of many researches worldwide. The preceding text has tried to summarize the different selective supramolecular aspects about their properties, structure, potential diversity, and applications to nonspecialized scientists. An introduction of these dendritic structures has combined a short description of the structure and synthesis with some historical perspectives, followed by a classification of dendritic structures, as covalent and noncovalent entities. Emphases have been given to their host-guest capacity to encapsulate small molecules, ions, or nanoparticles, as well as to interact with themselves or other nano-objects. The continued investigation in many fields of these unique architectures has produced a wide variety of branched fractal constructs, which undoubtedly will continue to spark the imagination of future synthetic architects. 

The first chapter by Bates and Gale provides an overview of the coordination of anions by synthetic organic hosts. The different organic functional groups used to bind anions are presented and this provides an introduction to the structural and electronic properties that hosts must have to recognise anionic guests. On the other hand, Bayly and Beer give a detailed account of the use of metal complexes as anion receptors. Besides the important structural features that metals can confer to receptors, their optical and redox properties make them attractive for the development of anion sensors. 

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