Tuning Mechanically Interlocked Molecules to Recognize Anions and Cations: A Computational Study

Abstract

Ions appear as active components in diverse materials. Here, the bonding energy between mechanically interlocked molecules (MIMs) or their acyclic/cyclic molecular derivatives and i) Cl À and Br À ions and/or ii) Na + and K + ions, have been investigated. The chemical environment provided by MIMs is less preferably to recognize ionic species compared to unconstrained interactions that are furnished by acyclic molecules. However, MIMs can be more adequate structures for ionic recognition than cyclic compounds if a chemical arrangement of the bond sites that relevantly support more favorable interactions with ions compared to Pauli repulsive ambient is provided. The hydrogen replacement by electron donor (À NH 2 ) or acceptor (À NO 2 ) groups in MIMs favors the anion/cation recognition due to decreased Pauli repulsion energy and/or more attractive non-covalent bonds. This study clarifies the chemical environment provided by MIMs to interact with ions and highlights these molecules as relevant structures to realize ionic sensing.

Exploiting the Mechanical Bond Effect for Enhanced Molecular Recognition and Sensing

“…Recent computational studies by Pereira Orenha et al corroborate the enhanced chloride binding properties of these rotaxane and catenane MIMs as arising due to the preorganized HB binding sites which line the MIM cavity. [62] The binding of halide anions by MIMs can also give rise to catalytic activity. In 2017, Leigh and co-workers demonstrated an interesting application of MIM co-conformational changes, with their report of dual-function switchable [2]rotaxane catalyst 13 (Figure 14).…”

“…corroborate the enhanced chloride binding properties of these rotaxane and catenane MIMs as arising due to the preorganized HB binding sites which line the MIM cavity. [ 62 ]…”