Synthesis, Structure, and Complexing Property of <i>p</i>-<i>tert</i>-Butylcalix[4]arene 1,3-Digallate

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 1H 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.