Metal Ion Binding to Calixarenes: Pendent Arm Coordination Assisted by Self-Inclusion

The synthesis and room-temperature single-crystal X-ray structural characterization of 25,27-di(allyloxy)-5,17-di-t-butyl-26,28-dimethoxycalix[4]arene are recorded. Crystals are monoclinic, C 2/c, a 29.089(5), b 10.742(2), c 26.218(8) angstrom, beta 110.09(2)-degrees, Z = 8; the structure was refined to a residual of 0.065 for 4103 independent 'observed' [I > 3sigma,(I)] reflections. The flattened partial cone conformation of the molecule allows inclusion of one of the methoxy substituents in a way which could block inclusion of a metal ion capable of polyhapto aromatic coordination and which may therefore explain why solution n.m.r. measurements indicate that silver(I) binds to the pendent alkene groups.