The solvent nature influence on the self-assembly of monosubstituted pillar[5]arenes containing N-(aminoalkyl)amide fragment

Chemistry of macrocyclic compounds is one of the rapidly developing areas of modern organic chemistry. These macrocycles have become widespread due to the high availability of parents compounds, the possibility of synthesis of ligands based on them for highly selective recognition, ion-selective membranes, electrodes, sensors and nanocontainers for targeted drug delivery. Moreover, in the past few years, attention of researchers has again been riveted on mechanically interlocked molecules (rotaxanes and pseudorotaxans) and supramolecular polymers, which can be explained by their potential application as molecular machines and materials. Mechanically interlocked molecules are molecular architectures consisting from two or more components which mechanically bind due to their own topology. Supramolecular polymers are comprise ordered monomer units combined via non-covalent bonds (hydrogen bonds or electrostatic interactions). Thus, this manuscript presents an approach to the synthesis of monosubstituted pillar[5]arenes containing N-(aminoalkyl)amide fragments with various substituent lengths. The formation of self-inclusion complexes by synthesized macrocycles was established by one- and two-dimensional NMR spectroscopy. According to NMR data, only four carbon atoms of the alkyl fragment were included in the macrocyclic cavity regardless of the alkyl chain length. Formation of self-inclusion complexes becomes possible due to the intramolecular hydrogen bond between the NH protons and the oxygen atom of methoxyl fragment, which is confirmed by IR spectroscopy. It was shown by dynamic light scattering that the synthesized pillar[5]arenes in chloroform form aggregates with an average hydrodynamic diameter of 316-640 nm and polydispersity index from 0.18 to 0.20, while polydisperse systems are formed in dimethyl sulfoxide.