Shaping calixarene frameworks. Synthesis and structure of a calix[8]arene containing three bridging phosphate units

The reaction of p-tert-butylcalix[8]arene with PCl5, followed by hydrolysis and subsequent esterification with triethyl orthoformate afforded a triphosphate involving all phenolic oxygen atoms of the calixarene framework. As revealed by an X-ray diffraction study, the presence of two μ3-(O,O,O) and one μ2-(O,O) bridging phosphoryl groups results in an unusual lengthening of the calix[8]arene loop (longest O⋯O separation: 13.9 Å)