A Density Functional Theory-Based Investigation of a pH- and Redox-Driven Tristable [2]Rotaxane in CH2Cl2 Dilute Solution.

A recently synthesized pH- and redox-driven tristable [2]rotaxane in dichloromethane solution (Angew. Chem. 2025, 64, e202414609) has been investigated within the framework of the Density Functional Theory DFT) in a polarizable and dielectric media via self-consistent reaction field method. Optimized molecular species are subsequently analyzed by combining converged wavefunctions with Quantum Theory of Atoms in Molecules (QTAIM) and the Independent Gradient Model based on Hirshfeld partition (IGMH) algorithms to characterize the nature of the chemical interactions modulating the preferential position of a 24-crown-8 (DB24C8) macrocycle over a responsive molecular thread containing three potential recognition moieties: an ammonium (AmH+), a bipyridinium (Bpy2+), and a triazolium (Trz+) moiety. Interestingly, the herein proposed computational investigation, while supporting the spectroscopically observed (1H NMR, 500 MHz, 298K) stable species under different equilibrium conditions, also sheds some light on the nature of the chemical interactions finely modulating the selective complexation pathways and the emerging shaping in dichloromethane.