Self-assembly and Anion Coordination Chemistry of Tripodal Scaffolds
1.5 Concluding remarks
In general, tripodal scaffolds with appropriately positioned hydrogen bonding groups can display exceptional self-assembling abilities. Notably, the functionalization of the tribenzylamine skeleton with one ureido group in every arm of the tripod leads to hydrogen bonded dimeric associations in solution and in the solid state. Furthermore, the tertiary amino group can be employed as a pH switch for the dimeric assembly-disassembly process.
In anion receptor chemistry, tris(2-aminoethyl)amine based tripodal urea/thiourea receptors have shown their high potential towards anion assisted capsule and pseudo-capsule formation. Higher coordination number of oxyanions like sulfate, phosphates and carbonate assist in dimeric capsular assembly formation while halides tend to form unimolecular capsules. On the other hand tripodal amide receptors on a benzene platform have shown their interest for recognition of hydrated anions, especially hydrated fluoride, via capsular assembly formation. Thus, a crucial task for going towards technological applications is the construction of molecular capsules for the recognition of hydrated anions rather than naked anions could be of better approach to target anions in natural environment. Capsular assemblies create a microenvironment with higher number of hydrogen bonding interaction sites that dictate the selectivity as well as assist to overcome the higher hydration energies of the anions. The recognition and binding of anions in molecular capsules is definitely a field which can expand considerably and bring immense advances in specialised applications such as: (a) removal and extraction of fluoride and other toxic anionic species from drinking water, (b) utilizing the binding and selectivity of the molecular capsules towards anionic species for the drug delivery applications, and (c) utilizing the molecular capsules as molecular reactors by stabilizing the anionic reactive intermediates inside the nanocavity.
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Chapter 2
Experimental methods and Characterization
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__________________________________________________________________ Chapter 2 In this chapter, a detailed report of the various reagents used in the synthesis of tripodal receptors, L1-L5 (Scheme 2.1), their synthetic procedures, crystallization details and specifications of instruments/equipments employed in the characterization of synthesized receptors and their various complexes with anions are presented.