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Supramolecular complexes of tetra-p-sulfonated calix [4]arene and racemic (alanine, histidine, and phenylalanine) and chiral ((S)-alanine, (S)-histidine, and (S)-tyrosine) amino acids have been isolated in the solid state and their molecular structures elucidated by X-ray diffraction studies. For alanine, histidine, and phenylalanine, racemic pairs of molecules are confined in capsules of tetra-p-sulfonated calix [4]arene in an overall bilayer arrangement. The (S)-amino acid isomers for alanine and histidine, however, formed 1:1 complexes within the bilayer arrangement found for many tetra-p-sulfonated calix[4]arene complexes. For (S)-tyrosine, a π-stacked chiral pair of isomers was encapsulated by tetra-p-sulfonated calix[4]arene.

As research on sustainable ammonia synthesis via electrochemical and photochemical N 2 reduction progresses to include a wider variety of aqueous and aprotic electrolytes, 1 H NMR spectroscopy is increasingly adopted as a means for ammonium quantification. However, this method is highly sensitive to experimental parameters, as demonstrated herein using a highly versatile and robust NMR pulse program. We demonstrate the sensitivity of the measurement to the final pH of the analyzed solution and identify a [H + ] concentration range enabling robust quantification. We compare direct quantification versus calibration approaches to show that the former is highly sensitive to spin relaxation effects and identify the latter as the most reliable approach. This method, when optimized, enables direct, rapid quantification of both 14 NH 4 + and 15 NH 4 + within 12−22 min. The limit of detection of 5−10 μM, depending on the solvent, which meets the needs of current electrochemical and photochemical N 2 reduction research.

The 1 : 1 p-But-calix[8]arene complex of C ~O is micelle-like, with a trimeric aggregate of fullerenes surrounded by three host molecules each in the double cone conformation, a structure that can accommodate one C70 unit by isomorphous replacement of one C60.

Charge-assisted p-stacking interactions result in the formation of large porous arrays formed from the inclusion of metal tris(phenanthroline) cations into p-sulfonatocalix-[4]arene anions.

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