Structural study of the novel deuterated calix[4]pyrrole complex d 12-meso-tetrakis(4-methoxyphenyl)-meso-tetramethylcalix[4]pyrrole–pyridine N-oxide–acetonitrile (1/1/1)

Abstract

Calix[4]pyrroles act as powerful receptors for electron-rich neutral guests and anionic guests in organic solvents. For the electron-rich neutral guest pyridine N-oxide, calix[4]pyrrole, with a deep cavity, provides an appropriate environment. The ability of calix[4]pyrrole to host binding guest molecules is the result of hydrogen bonding, π–π, C—H...π and hydrophobic interactions of the cavity. The novel title complex, C52H40D12N4O4·C5H5NO·C2H3N, based on d 12-meso-tetrakis(4-methoxyphenyl)-meso-tetramethylcalix[4]pyrrole, has been assembled using an excess of pyridine N-oxide and is the first deuterated complex of calix[4]pyrrole. A single-crystal X-ray study shows that the receptor adopts a cone conformation with the N-oxide fragment encapsulated deep within the cavity. 1H NMR spectroscopy was used to probe the molecular binding formation in CD3CN. The results are consistent with the single-crystal X-ray study in identifying that the pyridine N-oxide molecule occupies the cavity of the calix[4]pyrrole molecule. UV–vis spectroscopy revealed that the calix[4]pyrrole receptor molecules are able to form 1:1 inclusion complexes in CH3CN.