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 templates for 1,5-bridged calix[8]arenes 1H6–3H6, folding their skeleton in a ‘tub-shaped’ conformation composed of four 3/4-cone clefts. This templation occurs even for neutral 1H6 to give a (1H6Cs)+·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-π interactions can be excluded.