Scientists synthesized a chain of mechanically connected supramolecular units, capable of self-Assembly of organic monomers. Controlling the rate of heating of the reaction mixture and its composition, the authors obtained stable for several months catenary of nanoscale toroidal rings with a length of up to 22 units. A study published in the journal Nature.
Catenane called chain of two or more units-rings, not United chemically, but mechanically. The creation of such systems is highly non-trivial task. One approach to its solution is the development of molecules capable of forming loops, and at the same time coordinated with other molecules to create the longest chains. In the case where the ring is composed of a plurality of associated molecules supramolecular ensemble, their connection becomes particularly difficult. However, the study of such structures will lead to understanding non-trivial nontopological interactions and development of materials with special properties.
Sugata Datta (Sougata Datta) with colleagues from the University of Chiba synthesized nontopological structure of supramolecular rings with relatively large output. As a monomer were organic matter with non-polar areas which also contain atoms of oxygen and hydrogen associated with the nitrogen. The latter allowed the molecules to form with each other hydrogen bonds lining in a cyclic structure, which the authors called “socket” (rosette), six molecules of monomer. Connecting with each other in the stack, sockets formed segments of a torus with a radius of curvature of about 13 nanometers.
To monitor the kinetics of the process and ensure the desired formation of supramolecular rings, the authors regulate the rate of heating of the mixture and the composition of the solvent. A solution of monomers in a good (polar) solvent was poured into a ninefold volume of a less polar solvent. In the process of diffusion of new monomer in the solvent began supramolecular polymerization, as the environment of the molecules become less polar, favoring stacking.