Pillar[n]arenes and Other Cavitands: Aspects of Complex Thermodynamics

Abstract

Novel cavitands, the pillar[n]arenes, have captivated the attention of supramolecular chemists since the first reported synthesis of pillar[5]arene displaying binding capability to guest molecules. Recently, pillar[n]arenes and their functionalized pillar[n]arenes have been applied in many different areas, from supramolecular chemistry to materials science. Pillar[n]arenes have symmetric pillar shapes, and consist of n hydroquinone units bridged by methylene groups, which link the 2- and 5-positions of the hydroquinone units. The inner surface of the cavity of pillar[n]arenes is π-electron-rich, thus providing a favorable environment for guest molecules bearing electron withdrawing groups. Despite the extensive efforts, however, the complex thermodynamics of pillar[n]arenes have not been systematically investigated to date. This review outlines the range and perspectives of the thermodynamic characteristics of pillar[n]arenes in comparison with other successful cavitands, such as cyclodextrins and cucurbit[n]urils