Alkali cation "conformational templation" in 1,5-bridged calix[8]arenes: a single crystal x-ray proof

X-ray crystallography proves that alkali cations can act as conformational template for 1,5-bridged calix[8]arenes, folding their skeleton in a “tub- shaped” conformation composed by four 3/4-cone clefts. This templation occurs even for neutral 1,5-bridged calix[8]arenes, to give a (1,5- bridgedcalix[8]Cs+) •Cl– complex, where Cs+ was found perfectly fitting inside the eight calix[8]arene oxygens cavity. Conventional “electrostatic” coordination with O atoms occurs whereas cation-p interactions are excluded.