Cation-π interactions in caliX[n]arene and related systems

Non-covalent intermolecular forces have been recognized as a very important part of molecular interactions in complex biological systems. The fundamental functions of living matter such as transcription of genetic information in DNA, spatial arrangement of protein molecules, enzymatic functions or immunity system response are enabled owing to the presence of weak non-covalent forces based on hydrogen bonding interactions, van der Waals interactions, electrostatic interactions, hydrophobic effects, etc. Recently, among them so-called 'cation-π' interactions have been proved to contribute to the overall binding process in various artificial or biological systems. Calix[n]arenes have emerged as an important family of molecules with promising applications in many branches of chemistry. Because of their suitable molecular preorganization with aromatic units being 'concentrated' in a relatively small space, calix[n]arenes represent interesting compounds exhibiting an enhanced ability for cation-π interactions. The importance of such forces in calix[n]arene chemistry is demonstrated here on several recent examples.