Abstract
Conformational features of pyridine- and pyrimidine-based bistriazolyl anion receptors dissolved in acetonitrile-d3 were assessed by multidimensional, heteronuclear NMR spectroscopy. NOESY correlation signals suggested preorganization of both host molecules in solution in the absence of anions. In addition, only a single set of signals was observed in the 1H NMR spectra, which suggested a symmetrical conformation of anion receptors or their conformational exchange that is fast on the NMR time-scale. Furthermore, the predominant conformations of the pyridine- and pyrimidine-based anion receptors are preserved upon addition of chloride, bromide, and acetate anions. Chemical shift changes observed upon addition of anions showed that the NH (thio)urea and triazole protons are involved in anion-receptor interactions through hydrogen bonding.
Highlights
Small molecules that have appropriate functional groups or binding moieties may serve as sensors for anions, and this has been the focus of intensive research during the last decades.[1]
Only a single set of signals was observed in the 1H NMR spectra, which suggested a symmetrical conformation of anion receptors or their conformational exchange that is fast on the NMR time-scale
A single set of signals was observed for both triazole-urea moieties attached to C-2 and C-6 in the 1H NMR spectrum, which suggests a symmetrical conformation of both triazole moieties in host 1 or their conformational exchange that is fast on the NMR time-scale
Summary
Small molecules that have appropriate functional groups or binding moieties may serve as sensors for anions, and this has been the focus of intensive research during the last decades.[1]. Bistriazolyl anion receptors differ in their middle aromatic ring, compound 1 contains a pyridine and 2 contains a pyrimidine moiety (Figure 1). These two moieties could have a different effect on the preorganization, which is crucial to achieve high binding affinities of receptors. We were encouraged by the observations in our studies on indole anion receptors, which showed different conformational preferences in the absence and in the presence of anions.[12,13,14] The conformational preferences of bistriazolyl anion receptors and their complexes with anions were correlated with the electronic properties of pyridine, pyrimidine, triazole and (thio)urea moieties with the intention of obtaining new insight and give fresh stimulus to the design of anion-specific receptors
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
