ENGINEERING OF INTERMOLECULAR INTERACTIONS

ENGINEERING OF INTERMOLECULAR INTERACTIONS Idea of Molecular Surface (A)... 

Strong intermolecular interactions between active SCO mononuclear building blocks stem from the presence of efficient hydrogen-bonding networks or 7i-7i stacking interactions and have led to abrupt spin transitions [1], sometimes with associated hysteresis [2-4]. Despite the important efforts made by crystal engineers in establishing reliable connections between molecular and supramolecular structures on the basis of intermolecular interactions, the control of such forces is, however, difficult and becomes even more complicated when uncoordinated counter-ions and/or solvent molecules are present in the crystal lattice. 

The directed manipulation of intermolecular interactions (hydrogen bonding, van der Waals forces, metal coordination) gives access to a supramolecular engineering of molecular assemblies and of polymers (see, for instance, [7.10-7.13, 7.44, 9.142, 9.157, 9.161-9.163]) through the design of instructed monomeric and polymeric species. It leads to the development of a supramolecular materials chemistry (see Section 9.8). 

The determination of crystal structures by X-ray crystallography provides precise and unambiguous data on intermolecular interactions. Crystal engineering has been defined by Desiraju as the understanding of intermolecular interactions in the context of crystal packing and in the utilization of such knowledge in the design of new solids with desired physical and chemical properties. ... 

The physical properties of most nanomaterials are a manifestation of several types of interatomic, intramolecular, and intermolecular interactions, which can be either cooperative or competitive [17-21]. As a result, the magnitude of each interaction term in the nanomaterial of interest is either enhanced or depleted. In particular, judicious combination of various types of intermolecular interactions would lead to self-assembly process of given molecular systems including selfsynthesis, which would result in ideal molecular engineering process toward smart self-engineered functional molecular systems and nanomaterials. 

Among the most studied of intermolecular interactions is hydrogen bonding [1, 2]. The hydrogen bond plays a critical role in a myriad of biological processes and has been a cornerstone in the rapid development of fields such as self-assembly [3] and crystal engineering [4, 5]. 

The concepts of crystal engineering and molecular recognition are exceedingly similar and both fields are concerned with the manipulation of intermolecular interactions in the architecture of supramolecular assemblies. Crystal engineering and molecular recognition are the supramolecular equivalents of... 

The improved understanding of intermolecular interactions. hydrogen bonds in particular, is invaluable to the development of crystal engineering—an interdisciplinary area concerned with the rational design, synthesis, and assembly of functional materials through noncovalent interactions.Several aspects of this field are covered extensively elsewhere (see articles on hydrogen bonds. 

The crystal engineering community is also at the forefront of work into new kinds of intermolecular interactions. Recent single-crystal neutron diffraction studies revealed detailed information on OH-. -tc interactions " and on unconventional hydrogen bonds to metal center- as] well as MH-. HX-type interactions, where MH is a hydridic metal hydrogen moiety, and HX contains protic hydrogen. 

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