Synthesis, Structure, and Complexing Property of p-tert-Butylcalix

p-tert-Butylcalix[4]arene 1,3-digallate, which contains a nonbonded close contact between galloyl groups, was synthesized and its structure was determined by dynamic (1)H NMR and X-ray crystallography. The electronic spectra showed that a new absorption band of the complexes appeared at a longer wavelength region upon adding Ag(+) ion. This spectral shift was explained in terms of the interaction between the facing galloyl groups of the lower rim of the calixarene framework.