P-tert-Butylcalix[6]arene hexacarboxylic acid conformational switching and octahedral coordination with Pb(ii) and Sr(ii)

Article abstract of DOI:10.1039/c3cc48465c

p-tert-Butylcalix[6]arene hexaacetic acid is in a symmetric cone conformation in CHCl₃, but it becomes conformationally flexible in CHCl₃/CH₃CN (1:1). In this mixture the host has a strong binding affinity towards Pb(ii) and instantly forms a complex of low symmetry-shortly thereafter structural reorganization occurs resulting in a high symmetry complex of Pb(ii) in an octahedral cage of carboxylates. Sr(ii) and Ba(ii) display similar behavior over a longer period of time.