DESIGNING METAL-ORGANIC SUPERCONTAINERS FOR FUNCTIONAL APPLICATIONS: FROM SELECTIVE ANION BINDING TO SURFACE ENHANCED RAMAN SCATTERING

Synthetic container molecules that emulate biological structures and feature well-defined nanocavities have attracted tremendous interest among supramolecular chemists due to their promising potentials in ion recognition, catalysis, and chemical sensing. Our laboratory has developed a new class of container molecules, namely, metal-organic supercontainers (MOSCs), which feature both endo and exo cavities suitable for binding guest molecules. The overarching theme of this thesis was to use synthetic manipulations to modify the chemical structure and enhance the functional application of MOSCs in two specific areas, anion binding and chemical sensing. For the application of anion binding, we have designed and synthesized a new family of MOSCs based on the assembly of salicylhydroximate (Shi), carboxylate linkers, Ga(III), and lanthanide (III). Although constructed from a different set of chemical compositions that notably do not include a container precursor, the new Shi-MOSCs exhibit similar multi-cavity architectures but distinguish themselves from TBSC MOSCs with an overall negative charge. Interestingly, when modified with reactive moieties such as secondary amine (-NH-) group, the anionic Shi-MOSC demonstrates fluoride-selective anion binding, which is counterintuitive but can be attributed to the fluoride-targeting Lewis-basic and hydrogen-bonding functionalities of the -NH- group. A related Shi-MOSC functionalized with guanidinium group showed similar fluoride-binding selectivity, but its anion recognition can be further modulated by deprotonation of the guanidinium group. In a second application focusing on the design of new surface-enhanced Raman scattering (SERS) sensors, we modified prototypal TBSC MOSCs with carbonyl groups known to bind to gold nanoparticles (AuNPs). Ultraviolet-visible (UV-Vis) spectroscopic studies suggested that the carbonyl-functionalized MOSCs indeed bind to the AuNPs. We anticipate that the formation of ordered AuNP/MOSC assemblies will lead to the creation of hotspots, contributing to enhanced and reproduceable SERS sensing. Future studies will examine their SERS effects application in single-molecule detection of illicit substances