Preprint manuscript, including synthesis of new compounds and fluorescence/NMR-based binding data.
We present the synthesis and structure-activity relationships of sulfonatocalixarene hosts bearing novel substitutions. The calixarenes are modified on the upper rim at either one or two of the phenolic units, where the dual modifications are introduced selectively on neighboring or opposing phenols. The calixarenes are mono- or di-functionalized with nitro or formyl groups, with the remaining upper-rim sites in all cases occupied by sulfonates. Equilibrium association constants were determined between each host and the guests nicotine, nornicotine, and cotinine. Indicator displacement-based binding studies show that nicotine binds most strongly to the different members of the library followed by nornicotine, whereas cotinine displays weak to no binding. NMR titrations were carried out with nicotine and show different host-guest interaction geometries for the formyl-calixarenes versus the nitro-calixarenes.