A simple approach to generating in situ metal templated tris-(2-picolyl)amine-like multi-component assemblies with potential applications in molecular recognition and sensing is reported. The assembly is based on the reversible covalent association between di-(2-picolyl)amine and aldehydes. Zinc ion is the best for inducing assembly among the metal salts investigated, while 2-picolinaldehyde is the best among the heterocyclic aldehydes studied. Although an equilibrium constant of 6.6 * 103 M-1 was measured for the assembly formed by 2-picolinaldehdye, di-(2-picolyl)amine, and zinc triflate, the equilibrium constants for other systems are in the 102 M-1 range. X-ray structural analysis revealed that zinc adopts a trigonal bipyramidal geometry within the assembled ligand. The diversity and equilibrium of the assemblies are readily altered by simply changing concentrations, varying components, or adding counter anions.

The binding of the fluorescent polyanionic probe 5(6)-carboxyfluorescein (CF) to various generations of dendrimers (G3-G7) was studied in buffered aqueous media by absorbance and fluorescence spectroscopy and by isothermal titration calorimetry (ITC). Absorbance, fluorescence, and fluorescence anisotropy data were collected concurrently by using a multiwell plate format. Because ITC does not depend on the presence of a chromophore/fluorophore for measurement, it allowed the exploration of concentration ratios otherwise unattainable in the spectroscopy experiments. Qualitative dendrimer generational trends were observed and found to be consistent with dendrimer size and charge. However, a number of significant anomalies were found in the spectroscopic titration profiles, which led us to propose a binding model comprising multiple, concurrent binding regimes. The predictive value of the model was ascertained by construction of a binding simulation, which was consistent with the experimental results. Finally, ITC results afforded insights into the fundamental thermodynamic properties of the binding process along with trends found across dendrimer generations. Thermodynamic data were found to be in accordance with the proposed model.

Innovative models of teaching through research have broken the long-held paradigm that core chemistry competencies must be taught with predictable, scripted experiments. We describe here five fundamentally different, course-based undergraduate research experiences that integrate faculty research projects, accomplish ACS accreditation objectives, provide the benefits of an early research experience to students, and have resulted in publishable findings. The model detailed is the Freshman Research Initiative (FRI) at The University of Texas at Austin. While there are currently 30+ active FRI research groups, or “streams”, we focus this report on five different chemistry streams in these four areas (organic, inorganic, analytical, and biochemistry) to demonstrate how general chemistry laboratory skills are taught in the context of these varied research disciplines. To illustrate the flexibility of the FRI model for teaching first-year chemistry, we show how each stream teaches students three different skills within the context of their research: making (synthesis), measuring (UV-vis spectroscopy), and characterization. As a unifying example, all five chemistry streams describe using UV–vis spectroscopy to characterize new synthetic molecules, complexes, and compounds, followed by extensive quantitative collection, processing, and analysis of experimental data sets. The FRI model allows full integration of training in mandatory and accredited general chemistry skill sets with open-ended research experiences with unexpected outcomes in undergraduate science curricula. In turn, this model enables undergraduates to be productive contributors to new knowledge and scientific discovery at the earliest levels of the undergraduate experience.

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