The conformational exchange of 5,11,17,23-tetra-p-tert-butyl-25,27-di(N,N-diehtylaminocarbonyl)methoxy-26,28-dimethoxycalix[4]arene (1) and the complexation of the cesium cation by 1 in a binary mixture of deuterated acetonitrile and chloroform were studied by H-1, C-13, and Cs-133 NMR spectroscopy. The conformational interconversions of 1 were studied by H-1 2D EXSY NMR. The partial cone (pc) <-> cone (c) and the pc <-> pc self-interconversion of 1 are characterized by Delta H*: = 70 +/- 10 kJ/mol and Delta H* = 64 +/- 10 kJ/mol, respectively. The 1:1 complexes between the cesium cation and the c and pc conformer of 1 are described. The exchange between solvated Cs+ and the cone complex follows a purely dissociative mechanism, characterized by Delta H* = 89 +/- 2 kJ/mol and Delta S* = 71 +/- 4 J/(mol K).