Sheryl A. Tucker

Pyrogallol[4]arenes self-assemble to form stable hydrogen-bonded nanocapsules that have many unique properties making them potentially suitable for diverse applications, such as molecular transporters and nanoreactors. However, little is known about the host–guest behaviour of these materials. Utilizing nanoenvironment-dependent properties of the fluorescent reporter molecule, pyrene butanol (PBOH), the encapsulating abilities of the hexameric C-hexylpyrogallol[4]arene (PgC6) nanocages are further explored. Solution-state, spectroscopic and spectrofluorometric investigations and solid-state, single-crystal X-ray diffraction studies are in agreement and indicate an ordered inner phase. Up to two PBOH guest molecules are sequestered within the nanocapsule along with encapsulation solvent. The nature of the PBOH–PgC6 complex is found to change with time, as indicated by fluorophore leaching. These research findings provide additional insight into the encapsulation capabilities of PgCn nanocapsules.

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Selectivity of amine-terminated poly(amidoamine) (PAMAM-AT) dendrimers as host molecules for phenol blue and Nile red guests was investigated using absorption and fluorescence spectroscopies. Phenol blue has been known to associate near the core in the PAMAM-AT dendrimers. Nile red has also been shown to associate with this dendrimer family; however, this occurs in the outermost branches. Concentration ratios and generational dependencies were investigated. It was found that phenol blue was sequestered in the PAMAM-AT dendrimers in the presence of the interfering Nile red, and this association appeared to be the same as that of PAMAM-AT with phenol blue alone. As the concentration of Nile red increased relative to the concentration of phenol blue, the desired association of phenol blue became increasingly hindered. While the presence of Nile red did affect association, phenol blue still had considerable association even when Nile red was in ten-fold excess. The association of phenol blue with PAMAM-AT was stable and robust; however, Nile red's association was relatively weak and unstable.

Despite recent strides in the synthesis of elaborate nanometer-scale molecular hosts, the internal structure of these self-assembled cages remains ill characterized. We used fluorescent probe molecules, pyrene butyric acid (PBA), as guests in C -hexylpyrogallol[4]arene capsules to relay information about the chemical environment on the interior of the assemblies. Spectroscopic and single-crystal x-ray diffraction studies show that, in both solution and the solid state, the host can encapsulate two PBA guests and keep them well separated through specific interactions with the capsule walls.

The micellar liquid chromatographic (MLC) separations of polycyclic aromatic hydrocarbons (PAHs) were optimized for three micellar systems, cetyltrimethylammonium chloride (CTAC), dodecyltrimethylammonium chloride (DTAC), and sodium dodecylsulfate (SDS), with 1‐pentanol as the only organic additive. A difference in the separation was observed between CTAC and SDS/DTAC. Under each optimized separation conditions, CTAC‐modified mobile phase provides the least desirable separation, which is attributed to its longer carbon tail (C₁₆ vs. C₁₂). In addition to 1‐pentanol, the main organic additive, a second organic additive (3% 1‐propanol) in the micelle‐modified mobile phase was found to enhance the resolution of PAH chromatographic peaks. However, the extent of the enhancement varies for the different micellar systems, with the greatest resolution improvement seen for CTAC, and little effect for shorter‐tail SDS and DTAC. This study shows the potential use of second organic additive (1‐propanol), to the main nonpolar additive (1‐pentanol), in facilitating the MLC separation of larger nonpolar compounds.