Host–guest assembly of pyridinium-conjugated calix[4]arene via cation–π interaction

25-(4-Pyridiniumbutoxy)-26,27,28-trihydroxycalix[4]arene bromide 1 was designed to have both host and guest units in one molecule, and was assembled to become an oligomer via a cation–π interaction. X-ray diffraction (XRD) crystallographic study of 1 revealed that it oriented in a one-dimensional structure. Titrimetric 1H NMR analysis and electrospray ionization mass spectrometry (ESI-MS) analysis indicated that 1 formed an oligomer in solution, and the restraint of the segmental motion would lead to the stabilization of the cation–π interaction compared with a bi-molecular complex composed of 25,26,27,28-tetrahydroxycalix[4]arene and N-butylpyridinium bromide.