This paper deals with the ability ofp-tert-butylcalix[6]arene derivative1, which has six 3,6,9-trioxadecyl substituents at the phenolic oxygens, to encapsulate CT complexes of alkadienes with iodine. By adding I2to alkadienes in CH2Cl2in the presence of1, the absorbance at 363 nm, which was ascribed to I3−ion, increased in the order: 1,5-hexadiene<1,9-decadiene ≪1,7-octadiene. The reactivity features of the CT complexes in the presence of1are discus