cg900315h_si_005.cif (69.99 kB)

Organization of Lower Rim O-Alkylated p-Phosphonic Acid Calix[4]arenes

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posted on 05.08.2009, 00:00 by Thomas E. Clark, Mohamed Makha, Alexandre N. Sobolev, Dian Su, Henry Rohrs, Michael L. Gross, Colin L. Raston
Lower rim O-methyl, -n-butyl, and n-octadecyl calix[4]arenes bearing p-phosphonic acid groups on the upper rim have been prepared in high yield, compounds 1214. Where possible, the compounds have been characterized in the solid state using X-ray diffraction, or as the precursor phosphate esters or a cesium salt. The cone conformation ethyl phosphate ester for the octadecyl compound crystallizes in a bilayer 39.1 Å thick, which approaches the 40 Å of biological membranes. The 1,3-alternate cone conformation of the cesium salt of the O-methyl phosphonic acid has a metal ion coordinated to two methoxy groups, four O−P (two from neighboring calixarenes), and two η3-C3 moieties from two 1,3-disposed aromatic rings. MALDI-TOF spectra of compounds 1214 show successive peaks corresponding to 15, 33, and 16 calixarene units, which is consistent with the intramolecular H-bonding capabilities of the diprotic phosphonic acid groups where the calixarenes are arranged into layers, including bilayers.