ABSTRACT
In a minimalist case, a finite assembly of molecules will consist of two identical (i.e., homodimer) or different (i.e., heterodimer) molecules that interact via noncovalent forces [3]. The interactions propagate in a convergent fashion to give a discrete aggregate of molecules (Scheme 7.1). A major impetus to design and construct a finite assembly is to create a function not realized by the individual components [3]. In the liquid phase, a discrete assembly will be in equilibrium with its parts, as well as possible undesired complexes [3a]. The presence of such multiple equilibria will have an effect of reducing the structural integrity of the assembly and may require stronger intermolecular forces to hold the components together. It has been suggested that the sensitivity of multiple equilibria to subtle environmental factors
in the solution (e.g., solvent effects) can hinder the development of finite assemblies that exhibit designed and functional properties [3]. In the solid state, the structural integrity of a molecular assembly will be essentially maintained since the components are largely prohibited from dissociating back to individual parts. Inasmuch as the structure effects of multiple equilibria can hinder the formation of molecular assemblies in solution, subtle effects of crystal packing can hinder the formation of discrete molecular assemblies in solids. Although a variety of supramolecular interactions can be employed to control the molecules’ organization, finite assemblies generated in either the liquid phase or the solid state have been typically designed using the strength and directionality of hydrogen bonds [3].
